College Algebra (10th Edition)

Published by Pearson
ISBN 10: 0321979478
ISBN 13: 978-0-32197-947-6

Chapter 5 - Test - Page 399: 11

Answer

The inequality is valid for x-values less than 3 and x-values more than 8 (not including them) i.e. $(-\infty,3)\cap (8,\infty)$

Work Step by Step

First, we are going to move everything to the left side and simplify: $\dfrac{x+2}{x-3}<2$ $\dfrac{x+2}{x-3}-2<0$ $\dfrac{x+2}{x-3}-\dfrac{2(x-3)}{x-3}<0$ $\dfrac{x+2-(2x-6)}{x-3}<0$ $\dfrac{-x+8}{x-3}\leq0$ Now, we find critical points by equating the numerator and denominator to zero: $-x+8=0$ $x-3=0$ There are two critical points: $x_1=3$ $x_2=8$ Next, we are going to take three values: one less than 3; one between 3 and 8; and one more than 8 to test in the original equation and check if the inequality is true or not: First test with a value less than 3: $\dfrac{2+2}{2-3}<2$ $\dfrac{4}{-1}<2$ $-4<2 \rightarrow \text{ TRUE}$ Second test with a value between 3 and 8: $\dfrac{4+2}{4-3}<2$ $\dfrac{6}{1}<2$ $6<2 \rightarrow \text{ FALSE}$ Third test with a value more than 8: $\dfrac{13+2}{13-3}<2$ $\dfrac{15}{10}<2$ $1.5<2 \rightarrow \text{ TRUE}$ These tests show that the inequality $\dfrac{x+2}{x-3}<2$ is valid for values less than 3 and values more than 8 (not including them) i.e. $(-\infty,3)\cap (8,\infty)$
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