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: 11

Answer

$(-3, 3)$

Work Step by Step

$x^4 - 7x^2 - 18 < 0$ Find the roots of the function $(x^2 - 9) (x^2 + 2)< 0$ $(x+3)(x-3)(x^2 + 2)$ $x = -3, 3$ Test numbers in between those zero values to determine if the function is negative or positive (-∞, -3) $(-)(-)(+) = (+)$ (-3, 3) $(+)(-)(+) = (-)$ (3, ∞) $(+)(+)(+) = (+)$ Thus the solution is $(-3, 3)$
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