Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 3 - Section 3.7 - Polynomial and Rational Inequalities - 3.7 Exercises - Page 316: 25

Answer

$(-4, 3]$

Work Step by Step

$\frac{x^3 + 3x^2 - 9x - 27}{x+4} \leq 0$ $\frac{(x^2 - 9)(x + 3)}{x+4} \leq 0$ $\frac{(x - 3)(x + 3)^2}{x+4} \leq 0$ Find the zeros of the expressions in the numerator AND the denominator $x = 3, -3, -4$ Test numbers in between those zero values to determine if the function is negative or positive $(-∞, -4)$ $\frac{(-)(+))}{(-)} = (+)$ $(-4, -3]$ $\frac{(-)(+)}{(+)} = (-)$ $([-3, 3]$ $\frac{(-)(+)}{(+)} = (-)$ $[3, ∞)$ $\frac{(+)}{(+)(+)} = (+)$ Thus the solution is $(-4, 3]$
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