Given the inequality:
$$\log{\left(\frac{1}{2} \right)} \log{\left(\sqrt{5} \right)} \left(x - 4\right) > -1$$
To solve this inequality, we must first solve the corresponding equation:
$$\log{\left(\frac{1}{2} \right)} \log{\left(\sqrt{5} \right)} \left(x - 4\right) = -1$$
Solve:
Given the equation:
log(1/2)*log(sqrt(5))*(x-4) = -1
Expand expressions:
2*log(2)*log(5) - x*log(2)*log(5)/2 = -1
Reducing, you get:
1 + 2*log(2)*log(5) - x*log(2)*log(5)/2 = 0
Expand brackets in the left part
1 + 2*log2log5 - x*log2log5/2 = 0
Move free summands (without x)
from left part to right part, we given:
$$- \frac{x \log{\left(2 \right)} \log{\left(5 \right)}}{2} + 2 \log{\left(2 \right)} \log{\left(5 \right)} = -1$$
Divide both parts of the equation by (2*log(2)*log(5) - x*log(2)*log(5)/2)/x
x = -1 / ((2*log(2)*log(5) - x*log(2)*log(5)/2)/x)
We get the answer: x = 4 + 2/(log(2)*log(5))
$$x_{1} = \frac{2}{\log{\left(2 \right)} \log{\left(5 \right)}} + 4$$
$$x_{1} = \frac{2}{\log{\left(2 \right)} \log{\left(5 \right)}} + 4$$
This roots
$$x_{1} = \frac{2}{\log{\left(2 \right)} \log{\left(5 \right)}} + 4$$
is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
$$x_{0} < x_{1}$$
For example, let's take the point
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + \left(\frac{2}{\log{\left(2 \right)} \log{\left(5 \right)}} + 4\right)$$
=
$$\frac{2}{\log{\left(2 \right)} \log{\left(5 \right)}} + \frac{39}{10}$$
substitute to the expression
$$\log{\left(\frac{1}{2} \right)} \log{\left(\sqrt{5} \right)} \left(x - 4\right) > -1$$
$$\log{\left(\frac{1}{2} \right)} \log{\left(\sqrt{5} \right)} \left(-4 + \left(\frac{2}{\log{\left(2 \right)} \log{\left(5 \right)}} + \frac{39}{10}\right)\right) > -1$$
/ 1 2 \ / ___\
-|- -- + -------------|*log(2)*log\\/ 5 / > -1
\ 10 log(2)*log(5)/
the solution of our inequality is:
$$x < \frac{2}{\log{\left(2 \right)} \log{\left(5 \right)}} + 4$$
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