Many people think that exponential inequalities are something complex and incomprehensible. And that learning to solve them is almost a great art, which only the Chosen are able to comprehend...

Complete nonsense! Exponential inequalities are easy. And they are always resolved simply. Well, almost always. :)

Today we will look at this topic inside and out. This lesson will be very useful for those who are just beginning to understand this section of school mathematics. Let's start with simple problems and move on to more complex issues. There won’t be any hard work today, but what you’ll read now will be enough to solve most of the inequalities in all kinds of tests and independent work. And on this exam of yours too.

As always, let's start with the definition. An exponential inequality is any inequality that contains an exponential function. In other words, it can always be reduced to an inequality of the form

\[((a)^(x)) \gt b\]

Where the role of $b$ can be an ordinary number, or maybe something tougher. Examples? Yes please:

\[\begin(align) & ((2)^(x)) \gt 4;\quad ((2)^(x-1))\le \frac(1)(\sqrt(2));\ quad ((2)^(((x)^(2))-7x+14)) \lt 16; \\ & ((0,1)^(1-x)) \lt 0.01;\quad ((2)^(\frac(x)(2))) \lt ((4)^(\frac (4)(x))). \\\end(align)\]

I think the meaning is clear: there is an exponential function $((a)^(x))$, it is compared with something, and then asked to find $x$. In particularly clinical cases, instead of the variable $x$, they can put some function $f\left(x \right)$ and thereby complicate the inequality a little. :)

Of course, in some cases the inequality may appear more severe. For example:

\[((9)^(x))+8 \gt ((3)^(x+2))\]

Or even this:

In general, the complexity of such inequalities can be very different, but in the end they still reduce to the simple construction $((a)^(x)) \gt b$. And we will somehow figure out such a construction (in especially clinical cases, when nothing comes to mind, logarithms will help us). Therefore, now we will teach you how to solve such simple constructions.

Solving simple exponential inequalities

Let's consider something very simple. For example, this:

\[((2)^(x)) \gt 4\]

Obviously, the number on the right can be rewritten as a power of two: $4=((2)^(2))$. Thus, the original inequality can be rewritten in a very convenient form:

\[((2)^(x)) \gt ((2)^(2))\]

And now my hands are itching to “cross out” the twos in the bases of powers in order to get the answer $x \gt 2$. But before crossing out anything, let’s remember the powers of two:

\[((2)^(1))=2;\quad ((2)^(2))=4;\quad ((2)^(3))=8;\quad ((2)^( 4))=16;...\]

As you can see, the larger the number in the exponent, the larger the output number. "Thanks, Cap!" - one of the students will exclaim. Is it any different? Unfortunately, it happens. For example:

\[((\left(\frac(1)(2) \right))^(1))=\frac(1)(2);\quad ((\left(\frac(1)(2) \ right))^(2))=\frac(1)(4);\quad ((\left(\frac(1)(2) \right))^(3))=\frac(1)(8 );...\]

Here, too, everything is logical: the greater the degree, the more times the number 0.5 is multiplied by itself (i.e., divided in half). Thus, the resulting sequence of numbers is decreasing, and the difference between the first and second sequence is only in the base:

• If the base of degree $a \gt 1$, then as the exponent $n$ increases, the number $((a)^(n))$ will also increase;
• And vice versa, if $0 \lt a \lt 1$, then as the exponent $n$ increases, the number $((a)^(n))$ will decrease.

Summarizing these facts, we obtain the most important statement on which the entire solution of exponential inequalities is based:

If $a \gt 1$, then the inequality $((a)^(x)) \gt ((a)^(n))$ is equivalent to the inequality $x \gt n$. If $0 \lt a \lt 1$, then the inequality $((a)^(x)) \gt ((a)^(n))$ is equivalent to the inequality $x \lt n$.

In other words, if the base is greater than one, you can simply remove it - the inequality sign will not change. And if the base is less than one, then it can also be removed, but at the same time you will have to change the inequality sign.

Please note that we have not considered the options $a=1$ and $a\le 0$. Because in these cases uncertainty arises. Let's say how to solve an inequality of the form $((1)^(x)) \gt 3$? One to any power will again give one - we will never get three or more. Those. there are no solutions.

With negative reasons everything is even more interesting. For example, consider this inequality:

\[((\left(-2 \right))^(x)) \gt 4\]

At first glance, everything is simple:

Right? But no! It is enough to substitute a couple of even and a couple of odd numbers instead of $x$ to make sure that the solution is incorrect. Take a look:

\[\begin(align) & x=4\Rightarrow ((\left(-2 \right))^(4))=16 \gt 4; \\ & x=5\Rightarrow ((\left(-2 \right))^(5))=-32 \lt 4; \\ & x=6\Rightarrow ((\left(-2 \right))^(6))=64 \gt 4; \\ & x=7\Rightarrow ((\left(-2 \right))^(7))=-128 \lt 4. \\\end(align)\]

As you can see, the signs alternate. But there are also fractional powers and other nonsense. How, for example, would you order to calculate $((\left(-2 \right))^(\sqrt(7)))$ (minus two to the power of seven)? No way!

Therefore, for definiteness, we assume that in all exponential inequalities (and equations, by the way, too) $1\ne a \gt 0$. And then everything is solved very simply:

\[((a)^(x)) \gt ((a)^(n))\Rightarrow \left[ \begin(align) & x \gt n\quad \left(a \gt 1 \right), \\ & x \lt n\quad \left(0 \lt a \lt 1 \right). \\\end(align) \right.\]

In general, remember the main rule once again: if the base in an exponential equation is greater than one, you can simply remove it; and if the base is less than one, it can also be removed, but the sign of inequality will change.

Examples of solutions

So, let's look at a few simple exponential inequalities:

\[\begin(align) & ((2)^(x-1))\le \frac(1)(\sqrt(2)); \\ & ((0,1)^(1-x)) \lt 0.01; \\ & ((2)^(((x)^(2))-7x+14)) \lt 16; \\ & ((0,2)^(1+((x)^(2))))\ge \frac(1)(25). \\\end(align)\]

The primary task in all cases is the same: to reduce the inequalities to the simplest form $((a)^(x)) \gt ((a)^(n))$. This is exactly what we will now do with each inequality, and at the same time we will repeat the properties of degrees and exponential functions. So, let's go!

\[((2)^(x-1))\le \frac(1)(\sqrt(2))\]

What can you do here? Well, on the left we already have an indicative expression - nothing needs to be changed. But on the right there is some kind of crap: a fraction, and even a root in the denominator!

However, let us remember the rules for working with fractions and powers:

\[\begin(align) & \frac(1)(((a)^(n)))=((a)^(-n)); \\ & \sqrt[k](a)=((a)^(\frac(1)(k))). \\\end(align)\]

What does it mean? First, we can easily get rid of the fraction by turning it into a power with a negative exponent. And secondly, since the denominator has a root, it would be nice to turn it into a power - this time with a fractional exponent.

Apply these actions sequentially to the right side of the inequality and see what happens:

\[\frac(1)(\sqrt(2))=((\left(\sqrt(2) \right))^(-1))=((\left(((2)^(\frac( 1)(3))) \right))^(-1))=((2)^(\frac(1)(3)\cdot \left(-1 \right)))=((2)^ (-\frac(1)(3)))\]

Don't forget that when raising a degree to a power, the exponents of these degrees add up. And in general, when working with exponential equations and inequalities, it is absolutely necessary to know at least the simplest rules for working with powers:

\[\begin(align) & ((a)^(x))\cdot ((a)^(y))=((a)^(x+y)); \\ & \frac(((a)^(x)))(((a)^(y)))=((a)^(x-y)); \\ & ((\left(((a)^(x)) \right))^(y))=((a)^(x\cdot y)). \\\end(align)\]

Actually, we just applied the last rule. Therefore, our original inequality will be rewritten as follows:

\[((2)^(x-1))\le \frac(1)(\sqrt(2))\Rightarrow ((2)^(x-1))\le ((2)^(-\ frac(1)(3)))\]

Now we get rid of the two at the base. Since 2 > 1, the inequality sign will remain the same:

\[\begin(align) & x-1\le -\frac(1)(3)\Rightarrow x\le 1-\frac(1)(3)=\frac(2)(3); \\ & x\in \left(-\infty ;\frac(2)(3) \right]. \\\end(align)\]

That's the solution! The main difficulty is not at all in the exponential function, but in the competent transformation of the original expression: you need to carefully and quickly bring it to its simplest form.

Consider the second inequality:

\[((0.1)^(1-x)) \lt 0.01\]

So-so. Decimal fractions await us here. As I have said many times, in any expressions with powers you should get rid of decimals - this is often the only way to see a quick and simple solution. Here we will get rid of:

\[\begin(align) & 0.1=\frac(1)(10);\quad 0.01=\frac(1)(100)=((\left(\frac(1)(10) \ right))^(2)); \\ & ((0,1)^(1-x)) \lt 0,01\Rightarrow ((\left(\frac(1)(10) \right))^(1-x)) \lt ( (\left(\frac(1)(10) \right))^(2)). \\\end(align)\]

Here again we have the simplest inequality, and even with a base of 1/10, i.e. less than one. Well, we remove the bases, simultaneously changing the sign from “less” to “more”, and we get:

\[\begin(align) & 1-x \gt 2; \\ & -x \gt 2-1; \\ & -x \gt 1; \\& x \lt -1. \\\end(align)\]

We received the final answer: $x\in \left(-\infty ;-1 \right)$. Please note: the answer is precisely a set, and in no case a construction of the form $x \lt -1$. Because formally, such a construction is not a set at all, but an inequality with respect to the variable $x$. Yes, it is very simple, but it is not the answer!

Important Note. This inequality could be solved in another way - by reducing both sides to a power with a base greater than one. Take a look:

\[\frac(1)(10)=((10)^(-1))\Rightarrow ((\left(((10)^(-1)) \right))^(1-x)) \ lt ((\left(((10)^(-1)) \right))^(2))\Rightarrow ((10)^(-1\cdot \left(1-x \right))) \lt ((10)^(-1\cdot 2))\]

After such a transformation, we will again obtain an exponential inequality, but with a base of 10 > 1. This means that we can simply cross out the ten - the sign of the inequality will not change. We get:

\[\begin(align) & -1\cdot \left(1-x \right) \lt -1\cdot 2; \\ & x-1 \lt -2; \\ & x \lt -2+1=-1; \\ & x \lt -1. \\\end(align)\]

As you can see, the answer was exactly the same. At the same time, we saved ourselves from the need to change the sign and generally remember any rules. :)

\[((2)^(((x)^(2))-7x+14)) \lt 16\]

However, don't let this scare you. No matter what is in the indicators, the technology for solving inequality itself remains the same. Therefore, let us first note that 16 = 2 4. Let's rewrite the original inequality taking this fact into account:

\[\begin(align) & ((2)^(((x)^(2))-7x+14)) \lt ((2)^(4)); \\ & ((x)^(2))-7x+14 \lt 4; \\ & ((x)^(2))-7x+10 \lt 0. \\\end(align)\]

Hooray! We got the usual quadratic inequality! The sign has not changed anywhere, since the base is two - a number greater than one.

Zeros of a function on the number line

We arrange the signs of the function $f\left(x \right)=((x)^(2))-7x+10$ - obviously, its graph will be a parabola with branches up, so there will be “pluses” on the sides. We are interested in the region where the function is less than zero, i.e. $x\in \left(2;5 \right)$ is the answer to the original problem.

Finally, consider another inequality:

\[((0,2)^(1+((x)^(2))))\ge \frac(1)(25)\]

Again we see an exponential function with a decimal fraction at the base. Let's convert this fraction to a common fraction:

\[\begin(align) & 0.2=\frac(2)(10)=\frac(1)(5)=((5)^(-1))\Rightarrow \\ & \Rightarrow ((0 ,2)^(1+((x)^(2))))=((\left(((5)^(-1)) \right))^(1+((x)^(2) )))=((5)^(-1\cdot \left(1+((x)^(2)) \right)))\end(align)\]

In this case, we used the remark given earlier - we reduced the base to the number 5 > 1 in order to simplify our further solution. Let's do the same with the right side:

\[\frac(1)(25)=((\left(\frac(1)(5) \right))^(2))=((\left(((5)^(-1)) \ right))^(2))=((5)^(-1\cdot 2))=((5)^(-2))\]

Let us rewrite the original inequality taking into account both transformations:

\[((0,2)^(1+((x)^(2))))\ge \frac(1)(25)\Rightarrow ((5)^(-1\cdot \left(1+ ((x)^(2)) \right)))\ge ((5)^(-2))\]

The bases on both sides are the same and exceed one. There are no other terms on the right and left, so we simply “cross out” the fives and get a very simple expression:

\[\begin(align) & -1\cdot \left(1+((x)^(2)) \right)\ge -2; \\ & -1-((x)^(2))\ge -2; \\ & -((x)^(2))\ge -2+1; \\ & -((x)^(2))\ge -1;\quad \left| \cdot \left(-1 \right) \right. \\ & ((x)^(2))\le 1. \\\end(align)\]

This is where you need to be more careful. Many students like to simply take the square root of both sides of the inequality and write something like $x\le 1\Rightarrow x\in \left(-\infty ;-1 \right]$. Under no circumstances should this be done, since the root of an exact square is a modulus, and in no case an original variable:

\[\sqrt(((x)^(2)))=\left| x\right|\]

However, working with modules is not the most pleasant experience, is it? So we won't work. Instead, we simply move all the terms to the left and solve the usual inequality using the interval method:

$\begin(align) & ((x)^(2))-1\le 0; \\ & \left(x-1 \right)\left(x+1 \right)\le 0 \\ & ((x)_(1))=1;\quad ((x)_(2)) =-1; \\\end(align)$

We again mark the obtained points on the number line and look at the signs:

Please note: the dots are shaded

Since we were solving a non-strict inequality, all points on the graph are shaded. Therefore, the answer will be: $x\in \left[ -1;1 \right]$ is not an interval, but a segment.

In general, I would like to note that there is nothing complicated about exponential inequalities. The meaning of all the transformations that we performed today comes down to a simple algorithm:

• Find the basis to which we will reduce all degrees;
• Carefully perform the transformations to obtain an inequality of the form $((a)^(x)) \gt ((a)^(n))$. Of course, instead of the variables $x$ and $n$ there can be much more complex functions, but the meaning will not change;
• Cross out the bases of degrees. In this case, the inequality sign may change if the base $a \lt 1$.

In fact, this is a universal algorithm for solving all such inequalities. And everything else they will tell you on this topic is just specific techniques and tricks that will simplify and speed up the transformation. We’ll talk about one of these techniques now. :)

Rationalization method

Let's consider another set of inequalities:

\[\begin(align) & ((\text( )\!\!\pi\!\!\text( ))^(x+7)) \gt ((\text( )\!\!\pi \!\!\text( ))^(((x)^(2))-3x+2)); \\ & ((\left(2\sqrt(3)-3 \right))^(((x)^(2))-2x)) \lt 1; \\ & ((\left(\frac(1)(3) \right))^(((x)^(2))+2x)) \gt ((\left(\frac(1)(9) \right))^(16-x)); \\ & ((\left(3-2\sqrt(2) \right))^(3x-((x)^(2)))) \lt 1. \\\end(align)\]

So what's so special about them? They're light. Although, stop! Is the number π raised to some power? What nonsense?

How to raise the number $2\sqrt(3)-3$ to a power? Or $3-2\sqrt(2)$? The problem writers obviously drank too much Hawthorn before sitting down to work. :)

In fact, there is nothing scary about these tasks. Let me remind you: an exponential function is an expression of the form $((a)^(x))$, where the base $a$ is any positive number except one. The number π is positive - we already know that. The numbers $2\sqrt(3)-3$ and $3-2\sqrt(2)$ are also positive - this is easy to see if you compare them with zero.

It turns out that all these “frightening” inequalities are solved no different from the simple ones discussed above? And are they resolved in the same way? Yes, that's absolutely right. However, using their example, I would like to consider one technique that greatly saves time on independent work and exams. We will talk about the method of rationalization. So, attention:

Any exponential inequality of the form $((a)^(x)) \gt ((a)^(n))$ is equivalent to the inequality $\left(x-n \right)\cdot \left(a-1 \right) \gt 0 $.

That's the whole method. :) Did you think that there would be some kind of another game? Nothing like this! But this simple fact, written literally in one line, will greatly simplify our work. Take a look:

\[\begin(matrix) ((\text( )\!\!\pi\!\!\text( ))^(x+7)) \gt ((\text( )\!\!\pi\ !\!\text( ))^(((x)^(2))-3x+2)) \\ \Downarrow \\ \left(x+7-\left(((x)^(2)) -3x+2 \right) \right)\cdot \left(\text( )\!\!\pi\!\!\text( )-1 \right) \gt 0 \\\end(matrix)\]

So there are no more exponential functions! And you don’t have to remember whether the sign changes or not. But a new problem arises: what to do with the damn multiplier \[\left(\text( )\!\!\pi\!\!\text( )-1 \right)\]? We don’t know what the exact value of the number π is. However, the captain seems to hint at the obvious:

\[\text( )\!\!\pi\!\!\text( )\approx 3.14... \gt 3\Rightarrow \text( )\!\!\pi\!\!\text( )-1\gt 3-1=2\]

In general, the exact value of π does not really concern us - it is only important for us to understand that in any case $\text( )\!\!\pi\!\!\text( )-1 \gt 2$, t .e. this is a positive constant, and we can divide both sides of the inequality by it:

\[\begin(align) & \left(x+7-\left(((x)^(2))-3x+2 \right) \right)\cdot \left(\text( )\!\! \pi\!\!\text( )-1 \right) \gt 0 \\ & x+7-\left(((x)^(2))-3x+2 \right) \gt 0; \\ & x+7-((x)^(2))+3x-2 \gt 0; \\ & -((x)^(2))+4x+5 \gt 0;\quad \left| \cdot \left(-1 \right) \right. \\ & ((x)^(2))-4x-5 \lt 0; \\ & \left(x-5 \right)\left(x+1 \right) \lt 0. \\\end(align)\]

As you can see, at a certain moment we had to divide by minus one - and the sign of inequality changed. At the end, I expanded the quadratic trinomial using Vieta's theorem - it is obvious that the roots are equal to $((x)_(1))=5$ and $((x)_(2))=-1$. Then everything is solved using the classical interval method:

Solving inequality using the interval method

All points are removed because the original inequality is strict. We are interested in the region with negative values, so the answer is $x\in \left(-1;5 \right)$. That's the solution. :)

Let's move on to the next task:

\[((\left(2\sqrt(3)-3 \right))^(((x)^(2))-2x)) \lt 1\]

Everything here is generally simple, because there is a unit on the right. And we remember that one is any number raised to the zero power. Even if this number is an irrational expression at the base on the left:

\[\begin(align) & ((\left(2\sqrt(3)-3 \right))^(((x)^(2))-2x)) \lt 1=((\left(2 \sqrt(3)-3 \right))^(0)); \\ & ((\left(2\sqrt(3)-3 \right))^(((x)^(2))-2x)) \lt ((\left(2\sqrt(3)-3 \right))^(0)); \\\end(align)\]

Well, let's rationalize:

\[\begin(align) & \left(((x)^(2))-2x-0 \right)\cdot \left(2\sqrt(3)-3-1 \right) \lt 0; \\ & \left(((x)^(2))-2x-0 \right)\cdot \left(2\sqrt(3)-4 \right) \lt 0; \\ & \left(((x)^(2))-2x-0 \right)\cdot 2\left(\sqrt(3)-2 \right) \lt 0. \\\end(align)\ ]

All that remains is to figure out the signs. The factor $2\left(\sqrt(3)-2 \right)$ does not contain the variable $x$ - it is just a constant, and we need to find out its sign. To do this, note the following:

\[\begin(matrix) \sqrt(3) \lt \sqrt(4)=2 \\ \Downarrow \\ 2\left(\sqrt(3)-2 \right) \lt 2\cdot \left(2 -2 \right)=0 \\\end(matrix)\]

It turns out that the second factor is not just a constant, but a negative constant! And when dividing by it, the sign of the original inequality changes to the opposite:

\[\begin(align) & \left(((x)^(2))-2x-0 \right)\cdot 2\left(\sqrt(3)-2 \right) \lt 0; \\ & ((x)^(2))-2x-0 \gt 0; \\ & x\left(x-2 \right) \gt 0. \\\end(align)\]

Now everything becomes completely obvious. The roots of the square trinomial on the right are: $((x)_(1))=0$ and $((x)_(2))=2$. We mark them on the number line and look at the signs of the function $f\left(x \right)=x\left(x-2 \right)$:

The case when we are interested in side intervals

We are interested in the intervals marked with a plus sign. All that remains is to write down the answer:

Let's move on to the next example:

\[((\left(\frac(1)(3) \right))^(((x)^(2))+2x)) \gt ((\left(\frac(1)(9) \ right))^(16-x))\]

Well, everything is completely obvious here: the bases contain powers of the same number. Therefore, I will write everything briefly:

\[\begin(matrix) \frac(1)(3)=((3)^(-1));\quad \frac(1)(9)=\frac(1)(((3)^( 2)))=((3)^(-2)) \\ \Downarrow \\ ((\left(((3)^(-1)) \right))^(((x)^(2) )+2x)) \gt ((\left(((3)^(-2)) \right))^(16-x)) \\\end(matrix)\]

\[\begin(align) & ((3)^(-1\cdot \left(((x)^(2))+2x \right))) \gt ((3)^(-2\cdot \ left(16-x \right))); \\ & ((3)^(-((x)^(2))-2x)) \gt ((3)^(-32+2x)); \\ & \left(-((x)^(2))-2x-\left(-32+2x \right) \right)\cdot \left(3-1 \right) \gt 0; \\ & -((x)^(2))-2x+32-2x \gt 0; \\ & -((x)^(2))-4x+32 \gt 0;\quad \left| \cdot \left(-1 \right) \right. \\ & ((x)^(2))+4x-32 \lt 0; \\ & \left(x+8 \right)\left(x-4 \right) \lt 0. \\\end(align)\]

As you can see, during the transformation process we had to multiply by a negative number, so the inequality sign changed. At the very end, I again applied Vieta's theorem to factor the quadratic trinomial. As a result, the answer will be the following: $x\in \left(-8;4 \right)$ - anyone can verify this by drawing a number line, marking the points and counting the signs. Meanwhile, we will move on to the last inequality from our “set”:

\[((\left(3-2\sqrt(2) \right))^(3x-((x)^(2)))) \lt 1\]

As you can see, at the base there is again an irrational number, and on the right there is again a unit. Therefore, we rewrite our exponential inequality as follows:

\[((\left(3-2\sqrt(2) \right))^(3x-((x)^(2)))) \lt ((\left(3-2\sqrt(2) \ right))^(0))\]

We apply rationalization:

\[\begin(align) & \left(3x-((x)^(2))-0 \right)\cdot \left(3-2\sqrt(2)-1 \right) \lt 0; \\ & \left(3x-((x)^(2))-0 \right)\cdot \left(2-2\sqrt(2) \right) \lt 0; \\ & \left(3x-((x)^(2))-0 \right)\cdot 2\left(1-\sqrt(2) \right) \lt 0. \\\end(align)\ ]

However, it is quite obvious that $1-\sqrt(2) \lt 0$, since $\sqrt(2)\approx 1,4... \gt 1$. Therefore, the second factor is again a negative constant, into which both sides of the inequality can be divided:

\[\begin(matrix) \left(3x-((x)^(2))-0 \right)\cdot 2\left(1-\sqrt(2) \right) \lt 0 \\ \Downarrow \ \\end(matrix)\]

\[\begin(align) & 3x-((x)^(2))-0 \gt 0; \\ & 3x-((x)^(2)) \gt 0;\quad \left| \cdot \left(-1 \right) \right. \\ & ((x)^(2))-3x \lt 0; \\ & x\left(x-3 \right) \lt 0. \\\end(align)\]

Move to another base

A separate problem when solving exponential inequalities is the search for the “correct” basis. Unfortunately, it is not always obvious at the first glance at a task what to take as a basis, and what to do according to the degree of this basis.

But don’t worry: there is no magic or “secret” technology here. In mathematics, any skill that cannot be algorithmized can be easily developed through practice. But for this you will have to solve problems of different levels of complexity. For example, like this:

\[\begin(align) & ((2)^(\frac(x)(2))) \lt ((4)^(\frac(4)(x))); \\ & ((\left(\frac(1)(3) \right))^(\frac(3)(x)))\ge ((3)^(2+x)); \\ & ((\left(0,16 \right))^(1+2x))\cdot ((\left(6,25 \right))^(x))\ge 1; \\ & ((\left(\frac(27)(\sqrt(3)) \right))^(-x)) \lt ((9)^(4-2x))\cdot 81. \\\ end(align)\]

Difficult? Scary? It's easier than hitting a chicken on the asphalt! Let's try. First inequality:

\[((2)^(\frac(x)(2))) \lt ((4)^(\frac(4)(x)))\]

Well, I think everything is clear here:

We rewrite the original inequality, reducing everything to base two:

\[((2)^(\frac(x)(2))) \lt ((2)^(\frac(8)(x)))\Rightarrow \left(\frac(x)(2)- \frac(8)(x) \right)\cdot \left(2-1 \right) \lt 0\]

Yes, yes, you heard it right: I just applied the rationalization method described above. Now we need to work carefully: we have a fractional-rational inequality (this is one that has a variable in the denominator), so before equating anything to zero, we need to bring everything to a common denominator and get rid of the constant factor.

\[\begin(align) & \left(\frac(x)(2)-\frac(8)(x) \right)\cdot \left(2-1 \right) \lt 0; \\ & \left(\frac(((x)^(2))-16)(2x) \right)\cdot 1 \lt 0; \\ & \frac(((x)^(2))-16)(2x) \lt 0. \\\end(align)\]

Now we use the standard interval method. Numerator zeros: $x=\pm 4$. The denominator goes to zero only when $x=0$. There are three points in total that need to be marked on the number line (all points are pinned out because the inequality sign is strict). We get:

More complex case: three roots

As you might guess, the shading marks those intervals at which the expression on the left takes negative values. Therefore, the final answer will include two intervals at once:

The ends of the intervals are not included in the answer because the original inequality was strict. No further verification of this answer is required. In this regard, exponential inequalities are much simpler than logarithmic ones: no ODZ, no restrictions, etc.

Let's move on to the next task:

\[((\left(\frac(1)(3) \right))^(\frac(3)(x)))\ge ((3)^(2+x))\]

There are no problems here either, since we already know that $\frac(1)(3)=((3)^(-1))$, so the whole inequality can be rewritten as follows:

\[\begin(align) & ((\left(((3)^(-1)) \right))^(\frac(3)(x)))\ge ((3)^(2+x ))\Rightarrow ((3)^(-\frac(3)(x)))\ge ((3)^(2+x)); \\ & \left(-\frac(3)(x)-\left(2+x \right) \right)\cdot \left(3-1 \right)\ge 0; \\ & \left(-\frac(3)(x)-2-x \right)\cdot 2\ge 0;\quad \left| :\left(-2 \right) \right. \\ & \frac(3)(x)+2+x\le 0; \\ & \frac(((x)^(2))+2x+3)(x)\le 0. \\\end(align)\]

Please note: in the third line I decided not to waste time on trifles and immediately divide everything by (−2). Minul went into the first bracket (now there are pluses everywhere), and two was reduced with a constant factor. This is exactly what you should do when preparing real calculations for independent and test work - you don’t need to describe every action and transformation directly.

Next, the familiar method of intervals comes into play. Numerator zeros: but there are none. Because the discriminant will be negative. In turn, the denominator is reset only when $x=0$ - just like last time. Well, it is clear that to the right of $x=0$ the fraction will take positive values, and to the left - negative. Since we are interested in negative values, the final answer is: $x\in \left(-\infty ;0 \right)$.

\[((\left(0.16 \right))^(1+2x))\cdot ((\left(6.25 \right))^(x))\ge 1\]

What should you do with decimal fractions in exponential inequalities? That's right: get rid of them, converting them into ordinary ones. Here we will translate:

\[\begin(align) & 0.16=\frac(16)(100)=\frac(4)(25)\Rightarrow ((\left(0.16 \right))^(1+2x)) =((\left(\frac(4)(25) \right))^(1+2x)); \\ & 6.25=\frac(625)(100)=\frac(25)(4)\Rightarrow ((\left(6.25 \right))^(x))=((\left(\ frac(25)(4)\right))^(x)). \\\end(align)\]

So what did we get in the foundations of exponential functions? And we got two mutually inverse numbers:

\[\frac(25)(4)=((\left(\frac(4)(25) \right))^(-1))\Rightarrow ((\left(\frac(25)(4) \ right))^(x))=((\left(((\left(\frac(4)(25) \right))^(-1)) \right))^(x))=((\ left(\frac(4)(25) \right))^(-x))\]

Thus, the original inequality can be rewritten as follows:

\[\begin(align) & ((\left(\frac(4)(25) \right))^(1+2x))\cdot ((\left(\frac(4)(25) \right) )^(-x))\ge 1; \\ & ((\left(\frac(4)(25) \right))^(1+2x+\left(-x \right)))\ge ((\left(\frac(4)(25) \right))^(0)); \\ & ((\left(\frac(4)(25) \right))^(x+1))\ge ((\left(\frac(4)(25) \right))^(0) ). \\\end(align)\]

Of course, when multiplying powers with the same base, their exponents add up, which is what happened in the second line. In addition, we represented the unit on the right, also as a power in base 4/25. All that remains is to rationalize:

\[((\left(\frac(4)(25) \right))^(x+1))\ge ((\left(\frac(4)(25) \right))^(0)) \Rightarrow \left(x+1-0 \right)\cdot \left(\frac(4)(25)-1 \right)\ge 0\]

Note that $\frac(4)(25)-1=\frac(4-25)(25) \lt 0$, i.e. the second factor is a negative constant, and when dividing by it, the inequality sign will change:

\[\begin(align) & x+1-0\le 0\Rightarrow x\le -1; \\ & x\in \left(-\infty ;-1 \right]. \\\end(align)\]

Finally, the last inequality from the current “set”:

\[((\left(\frac(27)(\sqrt(3)) \right))^(-x)) \lt ((9)^(4-2x))\cdot 81\]

In principle, the idea of ​​the solution here is also clear: all exponential functions included in the inequality must be reduced to base “3”. But for this you will have to tinker a little with roots and powers:

\[\begin(align) & \frac(27)(\sqrt(3))=\frac(((3)^(3)))(((3)^(\frac(1)(3)) ))=((3)^(3-\frac(1)(3)))=((3)^(\frac(8)(3))); \\ & 9=((3)^(2));\quad 81=((3)^(4)). \\\end(align)\]

Taking these facts into account, the original inequality can be rewritten as follows:

\[\begin(align) & ((\left(((3)^(\frac(8)(3))) \right))^(-x)) \lt ((\left(((3) ^(2))\right))^(4-2x))\cdot ((3)^(4)); \\ & ((3)^(-\frac(8x)(3))) \lt ((3)^(8-4x))\cdot ((3)^(4)); \\ & ((3)^(-\frac(8x)(3))) \lt ((3)^(8-4x+4)); \\ & ((3)^(-\frac(8x)(3))) \lt ((3)^(4-4x)). \\\end(align)\]

Pay attention to the 2nd and 3rd lines of the calculations: before doing anything with the inequality, be sure to bring it to the form that we talked about from the very beginning of the lesson: $((a)^(x)) \lt ((a)^(n))$. As long as you have some left-handed factors, additional constants, etc. on the left or right, no rationalization or “crossing out” of grounds can be performed! Countless tasks have been completed incorrectly due to a failure to understand this simple fact. I myself constantly observe this problem with my students when we are just starting to analyze exponential and logarithmic inequalities.

But let's return to our task. Let's try to do without rationalization this time. Let us remember: the base of the degree is greater than one, so the triples can simply be crossed out - the inequality sign will not change. We get:

\[\begin(align) & -\frac(8x)(3) \lt 4-4x; \\ & 4x-\frac(8x)(3) \lt 4; \\ & \frac(4x)(3) \lt 4; \\ & 4x \lt 12; \\ & x \lt 3. \\\end(align)\]

That's all. Final answer: $x\in \left(-\infty ;3 \right)$.

Isolating a stable expression and replacing a variable

In conclusion, I propose solving four more exponential inequalities, which are already quite difficult for unprepared students. To cope with them, you need to remember the rules for working with degrees. In particular, putting common factors out of brackets.

But the most important thing is to learn to understand what exactly can be taken out of the brackets. Such an expression is called stable - it can be denoted by a new variable and thus get rid of the exponential function. So, let's look at the tasks:

\[\begin(align) & ((5)^(x+2))+((5)^(x+1))\ge 6; \\ & ((3)^(x))+((3)^(x+2))\ge 90; \\ & ((25)^(x+1.5))-((5)^(2x+2)) \gt 2500; \\ & ((\left(0.5 \right))^(-4x-8))-((16)^(x+1.5)) \gt 768. \\\end(align)\]

Let's start from the very first line. Let us write this inequality separately:

\[((5)^(x+2))+((5)^(x+1))\ge 6\]

Note that $((5)^(x+2))=((5)^(x+1+1))=((5)^(x+1))\cdot 5$, so the right-hand side can be rewrite:

Note that there are no other exponential functions except $((5)^(x+1))$ in the inequality. And in general, the variable $x$ does not appear anywhere else, so let’s introduce a new variable: $((5)^(x+1))=t$. We get the following construction:

\[\begin(align) & 5t+t\ge 6; \\&6t\ge 6; \\ & t\ge 1. \\\end(align)\]

We return to the original variable ($t=((5)^(x+1))$), and at the same time remember that 1=5 0 . We have:

\[\begin(align) & ((5)^(x+1))\ge ((5)^(0)); \\ & x+1\ge 0; \\ & x\ge -1. \\\end(align)\]

That's the solution! Answer: $x\in \left[ -1;+\infty \right)$. Let's move on to the second inequality:

\[((3)^(x))+((3)^(x+2))\ge 90\]

Everything is the same here. Note that $((3)^(x+2))=((3)^(x))\cdot ((3)^(2))=9\cdot ((3)^(x))$ . Then the left side can be rewritten:

\[\begin(align) & ((3)^(x))+9\cdot ((3)^(x))\ge 90;\quad \left| ((3)^(x))=t\right. \\&t+9t\ge 90; \\ & 10t\ge 90; \\ & t\ge 9\Rightarrow ((3)^(x))\ge 9\Rightarrow ((3)^(x))\ge ((3)^(2)); \\ & x\ge 2\Rightarrow x\in \left[ 2;+\infty \right). \\\end(align)\]

This is approximately how you need to draw up a solution for real tests and independent work.

Well, let's try something more complicated. For example, here is the inequality:

\[((25)^(x+1.5))-((5)^(2x+2)) \gt 2500\]

What's the problem here? First of all, the bases of the exponential functions on the left are different: 5 and 25. However, 25 = 5 2, so the first term can be transformed:

\[\begin(align) & ((25)^(x+1.5))=((\left(((5)^(2)) \right))^(x+1.5))= ((5)^(2x+3)); \\ & ((5)^(2x+3))=((5)^(2x+2+1))=((5)^(2x+2))\cdot 5. \\\end(align )\]

As you can see, at first we brought everything to the same base, and then we noticed that the first term can easily be reduced to the second - you just need to expand the exponent. Now you can safely introduce a new variable: $((5)^(2x+2))=t$, and the whole inequality will be rewritten as follows:

\[\begin(align) & 5t-t\ge 2500; \\&4t\ge 2500; \\ & t\ge 625=((5)^(4)); \\ & ((5)^(2x+2))\ge ((5)^(4)); \\ & 2x+2\ge 4; \\&2x\ge 2; \\ & x\ge 1. \\\end(align)\]

And again, no difficulties! Final answer: $x\in \left[ 1;+\infty \right)$. Let's move on to the final inequality in today's lesson:

\[((\left(0.5 \right))^(-4x-8))-((16)^(x+1.5)) \gt 768\]

The first thing you should pay attention to is, of course, the decimal fraction in the base of the first power. It is necessary to get rid of it, and at the same time bring all exponential functions to the same base - the number “2”:

\[\begin(align) & 0.5=\frac(1)(2)=((2)^(-1))\Rightarrow ((\left(0.5 \right))^(-4x- 8))=((\left(((2)^(-1)) \right))^(-4x-8))=((2)^(4x+8)); \\ & 16=((2)^(4))\Rightarrow ((16)^(x+1.5))=((\left(((2)^(4)) \right))^( x+1.5))=((2)^(4x+6)); \\ & ((2)^(4x+8))-((2)^(4x+6)) \gt 768. \\\end(align)\]

Great, we’ve taken the first step—everything has led to the same foundation. Now you need to select a stable expression. Note that $((2)^(4x+8))=((2)^(4x+6+2))=((2)^(4x+6))\cdot 4$. If we introduce a new variable $((2)^(4x+6))=t$, then the original inequality can be rewritten as follows:

\[\begin(align) & 4t-t \gt 768; \\ & 3t \gt 768; \\ & t \gt 256=((2)^(8)); \\ & ((2)^(4x+6)) \gt ((2)^(8)); \\ & 4x+6 \gt 8; \\ & 4x \gt 2; \\ & x \gt \frac(1)(2)=0.5. \\\end(align)\]

Naturally, the question may arise: how did we discover that 256 = 2 8? Unfortunately, here you just need to know the powers of two (and at the same time the powers of three and five). Well, or divide 256 by 2 (you can divide, since 256 is an even number) until we get the result. It will look something like this:

\[\begin(align) & 256=128\cdot 2= \\ & =64\cdot 2\cdot 2= \\ & =32\cdot 2\cdot 2\cdot 2= \\ & =16\cdot 2 \cdot 2\cdot 2\cdot 2= \\ & =8\cdot 2\cdot 2\cdot 2\cdot 2\cdot 2= \\ & =4\cdot 2\cdot 2\cdot 2\cdot 2\cdot 2\cdot 2= \\ & =2\cdot 2\cdot 2\cdot 2\cdot 2\cdot 2\cdot 2\cdot 2= \\ & =((2)^(8)).\end(align )\]

The same is true with three (the numbers 9, 27, 81 and 243 are its powers) and with seven (the numbers 49 and 343 would also be nice to remember). Well, the five also has “beautiful” degrees that you need to know:

\[\begin(align) & ((5)^(2))=25; \\ & ((5)^(3))=125; \\ & ((5)^(4))=625; \\ & ((5)^(5))=3125. \\\end(align)\]

Of course, if you wish, all these numbers can be restored in your mind by simply multiplying them successively by each other. However, when you have to solve several exponential inequalities, and each next one is more difficult than the previous one, then the last thing you want to think about is the powers of some numbers. And in this sense, these problems are more complex than “classical” inequalities that are solved by the interval method.

I hope this lesson helped you in mastering this topic. If something is unclear, ask in the comments. And see you in the next lessons. :)

Algebra and beginning of mathematical analysis. Grade 10. Textbook. Nikolsky S.M. and etc.

Basic and profile levels

8th ed. - M.: Education, 2009. - 430 p.

The textbook corresponds to the federal components of the state standard of general education in mathematics and contains material for both basic and specialized levels. You can work with it regardless of what textbooks schoolchildren studied from in previous years.

The textbook is aimed at preparing students for entering universities.

Format: djvu

Size: 15.2 MB

Watch, download:drive.google ; Rghost

Format: pdf

Size: 42.3 MB

Watch, download:drive.google ; Rghost

Note: PDF quality is better, almost excellent. Made from the same scan, 150 dpi, color. But in DJVU it turns out a little worse. This is a case where size matters.

TABLE OF CONTENTS
CHAPTER I. ROOTS, POWERS, LOGARITHMES
§ 1. Real numbers 3
1.1. Concept of real number 3
1.2. Lots of numbers. Properties of real numbers. ... 10
1.3*. Method of mathematical induction 16
1.4. Permutations 22
1.5. Placements 25
1.6. Combinations 27
1.7*. Proof of numerical inequalities 30
1.8*. Divisibility of integers 35
1.9*. Comparisons modulo t 38
1.10*. Problems with integer unknowns 40
§ 2. Rational equations and inequalities 44
2.1. Rational expressions 44
2.2. Newton's binomial formulas, sums and differences of powers. . 48
2.3*. Dividing polynomials with a remainder. Euclidean algorithm... 53
2.4*. Bezout's Theorem 57
2.5*. Root of the polynomial 60
2.6. Rational Equations 65
2.7. Systems of rational equations 70
2.8. Interval method for solving inequalities 75
2.9. Rational inequalities 79
2.10. Non-strict inequalities 84
2.11. Systems of rational inequalities 88
§ 3. Root of degree n 93
3.1. The concept of a function and its graph 93
3.2. Function y = x" 96
3.3. The concept of a root of degree n 100
3.4. Roots of even and odd powers 102
3.5. Arithmetic root 106
3.6. Properties of roots of degree l 111
3.7*. Function y = nx (x > 0) 114
3.8*. Function y = nVx 117
3.9*. Root n of the natural number 119
§ 4. Power of the positive number 122
4.1. Power with rational exponent 122
4.2. Properties of degrees with rational exponent 125
4.3. The concept of a sequence limit 131
4.4*. Properties of limits 134
4.5. Infinitely decreasing geometric progression. . . 137
4.6. Number e 140
4.7. The concept of a degree with an irrational exponent.... 142
4.8. Exponential function 144
§ 5. Logarithms 148
5.1. Concept of logarithm 148
5.2. Properties of logarithms 151
5.3. Logarithmic function 155
5.4*. Decimal logarithms 157
5.5*. Power functions 159
§ 6. Exponential and logarithmic equations and inequalities. . 164
6.1. The simplest exponential equations 164
6.2. Simple logarithmic equations 166
6.3. Equations reduced to the simplest by replacing the unknown 169
6.4. The simplest exponential inequalities 173
6.5. The simplest logarithmic inequalities 178
6.6. Inequalities reduced to the simplest by replacing the unknown 182
Historical information 187
CHAPTER II. TRIGONOMETRIC FORMULAS. TRIGONOMETRIC FUNCTIONS
§ 7. Sine and cosine of an angle 193
7.1. Concept of angle 193
7.2. Radian measure of angle 200
7.3. Determination of sine and cosine of an angle 203
7.4. Basic formulas for sin a and cos a 211
7.5. Arcsine 216
7.6. Arc cosine 221
7.7*. Examples of using arcsine and arccosine.... 225
7.8*. Formulas for arcsine and arccosine 231
§ 8. Tangent and cotangent of angle 233
8.1. Determination of tangent and cotangent of an angle 233
8.2. Basic formulas for tg a and ctg a 239
8.3. Arctangent 243
8.4*. Arc tangent 246
8.5*. Examples of using arctangent and arccotangent. . 249
8.6*. Formulas for arctangent and arccotangent 255
§ 9. Addition formulas 258
9.1. Cosine of the difference and cosine of the sum of two angles 258
9.2. Formulas for supplementary angles 262
9.3. Sine of the sum and sine of the difference of two angles 264
9.4. Sum and difference of sines and cosines 266
9.5. Formulas for double and half angles 268
9.6*. Product of sines and cosines 273
9.7*. Formulas for tangents 275
§ 10. Trigonometric functions of a numerical argument 280
10.1. Function y = sin x 281
10.2. Function y = cos x 285
10.3. Function y = tg * 288
10.4. Function y = ctg x 292
§ 11. Trigonometric equations and inequalities 295
11.1. Simple trigonometric equations 295
11.2. Equations reduced to the simplest by replacing the unknown 299
11.3. Applying Basic Trigonometric Formulas to Solving Equations 303
11.4. Homogeneous equations 307
11.5*. The simplest inequalities for sine and cosine.... 310
11.6*. The simplest inequalities for tangent and cotangent. . . 315
11.7*. Inequalities reduced to the simplest by replacing the unknown 319
11.8*. Introduction of auxiliary angle 322
11.9*. Replacing the unknown t = sin x + cos x 327
Historical information 330
CHAPTER III. ELEMENTS OF PROBABILITY THEORY
§ 12. Probability of event 333
12.1. The concept of event probability 333
12.2. Properties of event probabilities 338
§ 13*. Frequency. Conditional probability 342
13.1*. Relative frequency of event 342
13.2*. Conditional probability. Independent events 344
§ 14*. Expected value. Law of Large Numbers 348
14.1*. Mathematical expectation 348
14.2*. Difficult experience 353
14.3*. Bernoulli's formula. Law of Large Numbers 355
Historical information 359
REVIEW TASKS 362
Subject index 407
Replies 410

Place of work, position: - MOU-SOSH r.p. Pushkino, teacher

Region: — Saratov region

Characteristics of the lesson (session) Level of education: - secondary (complete) general education

Target audience: — Pupil (student)
Target audience: — Teacher (teacher)

Grade(s): – 10th grade

Subject(s): – Algebra

The purpose of the lesson: - didactic: to improve the basic techniques and methods for solving logarithmic and exponential inequalities and to ensure that all students master the basic algorithmic techniques for solving exponential and logarithmic inequalities; developmental: develop logical thinking, memory, cognitive interest, continue the formation of mathematical speech, develop the ability to analyze and compare; educational: to teach the aesthetic design of notes in a notebook, the ability to listen to others and the ability to communicate, instill accuracy and hard work.

Lesson type: – Lesson on generalization and systematization of knowledge

Students in class (audience): - 25

Brief description: - Solving exponential and logarithmic inequalities is considered one of the complex topics in mathematics and requires students to have good theoretical knowledge, the ability to apply them in practice, requires attention, hard work and intelligence. The topic discussed in the lesson is also taken up for entrance exams to universities and final exams. This type of lesson develops logical thinking, memory, cognitive interest, and helps develop the ability to analyze, compare and listen to others.

Lesson stages and their contents

Time

(min)

activity

teachers

student

1.Organizational stage

organizational

Absentees are reported.

2. Goal setting

Today in the lesson we will continue to practice the learned basic methods and methods for solving exponential and logarithmic inequalities, and also consider other ways to solve logarithmic and exponential inequalities: this is the transition to rational inequalities by replacing the unknown, as well as a method of dividing both sides of the inequality by a positive number.

Informs the topic of the lesson, the date of the lesson, the purpose of the lesson

Write down in notebooks

3.Checking homework

Calls 3 people to the board at the request of students, and at the same time conducts a frontal conversation on theoretical issues

Four people work at the board, the rest take part in a theoretical survey

For homework, you were asked to solve logarithmic and exponential inequalities at two levels of complexity. Let's see the solution to some of them on the board

6.49(a); 6.52(d) 6.56(b),6.54(b).

4.Updating students' knowledge

Let's remember what methods we discussed in the last lesson.

Today we will look at inequalities that, after introducing a new unknown, turn into rational inequalities.

To do this, let us remember what is the solution to a rational inequality of the form A(x) / B(x)>0? What method is used to solve rational inequalities?

5.Improving students' knowledge and skills

xx

Example1)2 - 9 / (2 -1)0

3 min

x +0.5xx +0.5

3). 25- 710+4>0

3 min

5). Consolidation of new things.

Doing exercises at the board

6.48(.g);6.58(b);6.59(b) -at the board 6.62(c)

Guides you to choose a rational solution method. monitors the correctness of reasoning and the correct recording of the solution to the inequality. Gives a grade for the work

One student decides at the board. The rest write down the solution in a notebook.

6) Differentiated independent work (Task on the screen)

Level 1:

Option 1 Option 2

No.6.48(b);No.6.48(e);

No. 6.58(a) ;No. 6.58(c)

Level 2:

Option 1 Option 2

No.6.61(b);No.6.61(d);

No. 6.62(c); No. 6.62(d).

5 minutes

2 people work individually on a side board. The rest perform multi-level independent work in the field

7)Checking independent work

3 min

8)Homework (on screen)

1st level clause 6.6; No. 6.48 (a.); No. 6.57 (1 st); No. 6.50 (a).

Level 2: clause 6.6; No. 6.59(c); No. 6.62 (a); No. 158 (p. 382); No. 168 (a, b) (p. 383)

2 minutes

Explains homework, drawing students' attention to the fact that similar tasks have been covered in class.

The last two tasks were offered upon admission to Moscow State University and MTITF.

After listening carefully to the teacher, write down your homework. You choose the difficulty level yourself.

8) Summing up the lesson: Solving exponential and logarithmic inequalities is considered one of the complex topics of the school mathematics course and requires students to have good theoretical knowledge, the ability to apply them in practice, requires attention, hard work, and intelligence; it is for this reason that the inequalities discussed in the lesson are included in the introductory exams for universities and final exams. Today in class everyone worked very well and received the following marks

Thanks to all.

2 minutes

Files:
File size: 6789120 bytes.

Mathematics teacher Municipal Educational Institution - Secondary School No. 2, Stepnoe Trufyakova Galina Ivanovna website

Slide 2

Lesson summary

The topic Exponential Inequalities is an essential topic in Mathematics. According to the textbook by S. M. Nikolsky, it is studied in the 10th grade and 2 hours are allocated for its study in planning: 1 hour - The simplest exponential inequalities; 1 hour – Inequalities reduced to the simplest by replacing the unknown. During this time, it is necessary to introduce students to new and very voluminous material, teach them to solve all types of exponential inequalities and practice these skills and abilities well. Therefore, lessons in the formation of new knowledge in the form of lectures using information and communication technology allow solving these problems quickly and with greater efficiency. success.

Slide 3

Slide 4

Albert Einstein

“I have to divide my time between politics and solving equations and inequalities. However, solving equations and inequalities, in my opinion, is much more important, because politics exists only for this moment, but equations and inequalities will exist forever.”

Slide 5

Lesson structure

Organizational moment Setting goals and objectives Lecture plan Updating students' knowledge in the form of repeating previously studied material Introduction of new knowledge Consolidating knowledge in the form of an interview Summing up the lesson Homework

Slide 6

Organizing time

Greet students Mark the names of students absent from class in the class register

Slide 7

Setting goals and objectives

Announce to students at the beginning of the lesson its goals and objectives. Introduce students to the lecture plan and write it down in their notebooks.

Slide 8

Lesson Objectives

Educational Formation of the concept of exponential inequalities Familiarization of students with the types of exponential inequalities Formation of skills and abilities for solving exponential inequalities

Slide 9

Educational Cultivating hard work Cultivating independence in achieving goals Forming computational skills Forming aesthetic skills when making notes

Slide 10

Developmental Development of mental activity Development of creative initiative Development of cognitive activity Development of speech and memory

Slide 11

Lesson Objectives

Review the properties of the exponential function Review the rules for solving quadratic and fractional rational inequalities Work out the algorithm for solving the simplest exponential inequalities Teach students to distinguish between types of exponential inequalities Teach students to solve exponential inequalities

Slide 12

Lesson type

Lesson in the formation of new knowledge

Slide 13

Lesson type

Lesson - lecture

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Teaching methods

Explanatory and illustrative Heuristic Search Problematic

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Education technology

Information and communication technology based on problem-based learning

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Lecture outline

Repetition of the properties of the exponential function The simplest exponential inequalities Exponential inequalities that reduce to the simplest Exponential inequalities that reduce to quadratic inequalities Homogeneous exponential inequalities of the first degree Homogeneous exponential inequalities of the second degree Exponential inequalities that reduce to rational inequalities Exponential non-standard inequalities

Slide 17

Repetition of previously studied material

Solve on the board and in notebooks: a) quadratic inequalities: x² – 2x – 1≥0 x² – 2x - 3 ≤0 b) fractional rational inequality: (x – 5) \ (x - 2) ≤ 0

Slide 18

Repetition of properties of exponential function

Slide 19

decreases monotonically on R The Ox axis is a horizontal asymptote monotonically increases on R 8. For any real values ​​of x and y; a>0, a≠1; b>0, b≠1. 7. Asymptote 6. Extrema 5. Monotonicity 4. Even, odd 3. Intervals for comparing the values ​​of a function with unity 2. Range of values ​​of a function 1 Range of definition of a function Properties of an exponential function Exponential inequalities, their types and methods of solution Exponential function has no extrema. The function is neither even nor odd (a function of general form).

Slide 20

Exponential inequalities, their types and methods for solving Task No. 1 Find the domain of definition of the function

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Exponential inequalities, their types and methods for solving Task No. 2 Determine the values

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Exponential inequalities, their types and methods for solving Task No. 3 Determine the type of function increasing decreasing increasing decreasing

Slide 23

Introduction of new knowledge

Slide 24

Exponential inequalities, their types and methods of solution DEFINITION of the simplest exponential inequalities: Let a be a given positive number not equal to one and b be a given real number. Then the inequalities ax>b (ax≥b) and ax

Slide 25

Exponential inequalities, their types and methods of solving WHAT IS solving an inequality called? The solution to an inequality with an unknown x is the number x0, which, when substituted into the inequality, produces a true numerical inequality.

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Exponential inequalities, their types and methods of solution WHAT DOES IT MEAN to solve an inequality? Solving an inequality means finding all its solutions or showing that there are none.

Slide 27

Let's consider the relative position of the graph of the function y=ax, a>0, a≠1and the straight line y=b. Exponential inequalities, their types and methods of solution y x y x y=b, b 0 y=b, b>0 0 1 0 1 x0 x0

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Exponential inequalities, their types and methods of solution CONCLUSION No. 1: When b≤0, the straight line y=b does not intersect the graph of the function y=ax, because is located below the curve y=ax, therefore the inequalities ax>b(ax≥b) are satisfied for xR, and the inequalities ax

Slide 29

CONCLUSION No. 2: y x ​​0 x0 x1 y=b, b>0 x2 Exponential inequalities, their types and methods of solution If a>1 and b > 0, then for each x1 x0- below the straight line y=b. 1 For b> 0, the straight line y = b intersects the graph of the function y = ax at a single point, the abscissa of which is x0 = logab

Slide 30

CONCLUSION No. 2: y x ​​0 x0 x1 y=b, b>0 1 Exponential inequalities, their types and methods of solution If a>1 and b > 0, then for each x1 >x0 the corresponding point of the graph of the function y=ax is located above the straight line y=b, and for for each x2 0 the straight line y = b intersects the graph of the function y = ax at a single point, the abscissa of which is x0 = logab x2

Slide 31

The simplest exponential inequalities Exponential inequalities, their types and methods of solution

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Exponential inequalities, their types and methods of solution Example No. 1.1 Answer: increases over the entire domain of definition, Solution:

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Exponential inequalities, their types and methods of solution Example No. 1.2 Solution: Answer: decreases over the entire domain of definition,

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Exponential inequalities, their types and methods of solution Example No. 1.3 Solution: Answer: increases over the entire domain of definition,

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Exponential inequalities, their types and methods for solving Types of exponential inequalities and methods for solving them 1) Exponential inequalities, reducing to the simplest ones, increase over the entire domain of definition Example No. 1 Answer: Solution:

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Exponential inequalities, their types and methods of solution Example No. 1.4 Solution: increases over the entire domain of definition, Answer:

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Exponential inequalities, their types and methods for solving Types of exponential inequalities and methods for solving them Exponential inequalities, reduced to the simplest Example No. 2 increases over the entire domain of definition Answer: Solution:

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Exponential inequalities, their types and methods for solving Types of exponential inequalities and methods for solving them 2) Exponential inequalities, reducing to quadratic inequalities Example Let's return to the variable x increases for all x from the domain of definition Answer: Solution:

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Exponential inequalities, their types and methods for solving Types of exponential inequalities and methods for solving them 3) Homogeneous exponential inequalities of the first and second degree. Homogeneous exponential inequalities of the first degree Example No. 1 increases over the entire domain of definition Answer: Solution:

Exponential inequalities, their types and methods for solving Types of exponential inequalities and methods for solving them 4) Exponential inequalities, reducing to rational inequalities Example Let's return to the variable x increases over the entire domain of definition Answer: Solution:

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Exponential inequalities, their types and methods for solving Types of exponential inequalities and methods for solving them 5) Exponential non-standard inequalities Example Solution: Let's solve each statement of the set separately. Inequality equals aggregate

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Exponential inequalities, their types and methods for solving Types of exponential inequalities and methods for solving them 5) Exponential non-standard inequalities Example Answer: Solution: Check The check showed that x=1, x=3, x=1.5 are solutions to the equation, and x=2 is not a solution to the equation. So,

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Consolidation of knowledge

What inequalities are called exponential? When does an exponential inequality have a solution for any value of x? When does an exponential inequality have no solutions? What types of inequalities did you learn in this lesson? How are the simplest inequalities solved? How are inequalities that reduce to quadratic inequalities solved? How are homogeneous inequalities solved? How are inequalities that can be reduced to rational ones resolved?

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Lesson Summary

Find out what new students learned in this lesson Give grades to students for their work in the lesson with detailed comments

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Homework

Textbook for grade 10 “Algebra and beginnings of analysis” author S.M. Nikolsky Study paragraphs 6.4 and 6.6, No. 6.31-6.35 and No. 6.45-6.50 solve

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Exponential inequalities, their types and methods of solution

Topic 6. Exponential and logarithmic equations and inequalities (11 hours)
Lesson topic. Inequalities reduced to the simplest by replacing the unknown.
Purpose of the lesson: To develop skills in solving exponential and logarithmic inequalities, by reducing them to the simplest, by replacing the unknown.
Tasks:
Educational: repeat and consolidate knowledge on the topic “solving the simplest exponential and logarithmic inequalities”, learn to solve logarithmic and exponential inequalities using the substitution method.
Developmental: to develop the student’s ability to identify two types of inequality and determine ways to solve them (logical and intuitive thinking, justification of judgments, classification, comparison), to develop skills of self-control and self-test, the ability to move according to a given algorithm, evaluate and correct the result obtained.
Educational: continue to develop such qualities of students as: the ability to listen to each other; the ability to exercise mutual control and self-esteem.
Lesson type: combined.
Textbook Algebra grade 10 S.M. Nikolsky, M.K. Potapov, N.N. Reshetnikov, A.V. Shevkin
During the classes
Organizing time.
Checking homework.
Updating basic knowledge.
Frontal:
1. What inequalities are called the simplest exponential inequalities?
2. Explain the meaning of solving simple exponential inequalities.
3. What inequalities are called the simplest logarithmic inequalities?
4. Explain the meaning of solving simple logarithmic inequalities.
With writing on the board (1 student each):
Solve inequalities
2x<1160,3х<103log2x>5log15x>-2Explanation of new material and its step-by-step reinforcement.
1.1. Explanation of new material.
1. Solve the inequality:
2x2-3x<14Пусть х2-3х=t, тогда
2t<142t<2-2т. к. основание 2>1, then
t<-2Обратная замена:
x2-3x<-2х2-3х+2<0Нахдим его корни: x1=1, x2=2Отмечаем эти точки на координатной прямой и выясняем знак выражения x2−3x+2 на каждом из полученных интервалов.
We are interested in the sign "−−". Then we get
Answer:x∈(1;2)
2. Solve the inequality

1.2. Step-by-step consolidation.
No. 6.49(a, c).
No. 6.52(d).
a) 74x2-9x+6>74x2-9x+6>14x2-9x+5>0x1=5/4 x2=1
Answer: -∞;1∪54;+∞в) (13)5х2-4х-3>95х2-4х-3<-25х2-4х-1<0x1=-15 x2=1
Answer: -15;1d) log5x2-2x-3<1
log5x2-2x-3 00<х2-2х-3<5х2-2х-3<5х2-2х-3>0 x2-2x-8<0х2-2х-3>0

Answer: -2;-1∪3;42.1. Explanation of new material.
3. Solve the inequality

Then 1 inequality makes sense for all x, and the second

2.2. Step-by-step consolidation.
Solve inequality No. 6.56(c)
3.1. Explanation of new material.
4. Solve the inequality

3.2. Step-by-step consolidation.
Solve inequality No. 6.60(a)
Summing up the lesson.
Reflection.
Homework.
P. 6.6
No. 6.49 (b, d)
No. 6.52 (a, b)
No. 6.56 (d)
No. 6.60 (b)

Attached files