Solution assignment 08 Inequalities with fractions

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Assignment 8

Solve:

\displaystyle\frac{2x}{x+2}>3

Solution

The best way to solve such an inequality is to make the right-hand side equal to 0. So we take 3 to the left-hand side and convert the fractions to the same denominator.

\displaystyle\frac{2x}{x+2}-3\displaystyle\frac{x+2}{x+2}>0

\displaystyle\frac{2x-3x-6}{x+2}>0

\displaystyle\frac{x+6}{x+2}<0

For both the numerator and the denominator we draw number lines, as well as for the quotient.

x+6 ---------------(-6)++++++++++++++
x+2 --------------------------------(-2)+++++
quotient  +++++++(-6)------------(-2)+++++

The third line shows that the inequality is satisfied if:

-6<x<-2

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