College Algebra (10th Edition)

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

Chapter 5 - Section 5.4 - Polynomial and Rational Inequalities - 5.4 Assess Your Understanding - Page 373: 39

Answer

The inequality $\dfrac{x+4}{x-2}\leq1$ is valid for values only less than 2 (not including it) i.e. $(-\infty,2)$

Work Step by Step

First, we are going to move everything to the left side and simplify: $\dfrac{x+4}{x-2}\leq1$ $\dfrac{x+4}{x-2}-1\leq0$ $\dfrac{x+4}{x-2}-\dfrac{x-2}{x-2}\leq0$ $\dfrac{x+4-(x-2)}{x-2}\leq0$ $\dfrac{6}{x-2}\leq0$ Now, we find critical points by equating the numerator and denominator to zero: $6=0$ $x-2=0$ There is only one critical point: $x=2$ Next, we are going to take two values: one less than 2 and one more than 2 to test in the original equation and check if the inequality is true or not: First test with a value less than 2: $\dfrac{0+4}{0-2}\leq1$ $\dfrac{4}{-2}\leq1$ $-2\leq1 \rightarrow \text{ TRUE}$ Second test with a value more than 2: $\dfrac{3+4}{3-2}\leq1$ $\dfrac{7}{1}\leq1$ $7\leq1 \rightarrow \text{ FALSE}$ These tests show that the inequality $\dfrac{x+4}{x-2}\leq1$ is valid for values only less than 2 (not including it) i.e. $(-\infty,2)$
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