Mister Exam

log½x≤−3. inequation

A inequation with variable

The solution

You have entered [src]
log(1/2)*x <= -3
$$x \log{\left(\frac{1}{2} \right)} \leq -3$$
x*log(1/2) <= -3
Detail solution
Given the inequality:
$$x \log{\left(\frac{1}{2} \right)} \leq -3$$
To solve this inequality, we must first solve the corresponding equation:
$$x \log{\left(\frac{1}{2} \right)} = -3$$
Solve:
Given the linear equation:
log(1/2)*x = -3

Expand brackets in the left part
log1/2x = -3

Divide both parts of the equation by -log(2)
x = -3 / (-log(2))

$$x_{1} = \frac{3}{\log{\left(2 \right)}}$$
$$x_{1} = \frac{3}{\log{\left(2 \right)}}$$
This roots
$$x_{1} = \frac{3}{\log{\left(2 \right)}}$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$x_{0} \leq x_{1}$$
For example, let's take the point
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + \frac{3}{\log{\left(2 \right)}}$$
=
$$- \frac{1}{10} + \frac{3}{\log{\left(2 \right)}}$$
substitute to the expression
$$x \log{\left(\frac{1}{2} \right)} \leq -3$$
$$\left(- \frac{1}{10} + \frac{3}{\log{\left(2 \right)}}\right) \log{\left(\frac{1}{2} \right)} \leq -3$$
 /  1      3   \             
-|- -- + ------|*log(2) <= -3
 \  10   log(2)/             

but
 /  1      3   \             
-|- -- + ------|*log(2) >= -3
 \  10   log(2)/             

Then
$$x \leq \frac{3}{\log{\left(2 \right)}}$$
no execute
the solution of our inequality is:
$$x \geq \frac{3}{\log{\left(2 \right)}}$$
         _____  
        /
-------•-------
       x1
Solving inequality on a graph
Rapid solution 2 [src]
   3        
[------, oo)
 log(2)     
$$x\ in\ \left[\frac{3}{\log{\left(2 \right)}}, \infty\right)$$
x in Interval(3/log(2), oo)
Rapid solution [src]
   /  3                \
And|------ <= x, x < oo|
   \log(2)             /
$$\frac{3}{\log{\left(2 \right)}} \leq x \wedge x < \infty$$
(x < oo)∧(3/log(2) <= x)