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: 16

Answer

$[-1/3, 1/2] U [1, ∞ )$

Work Step by Step

$x^2 (7-6x) \leq 1$ Find the roots of the function $7x^2 - 6x^3 - 1 \leq 0$ From the graph attached below with the zeros highlighted, the zeros are at: $x = -1/3, 1/2, 1$ Thus the factored equation is $(-3x - 1)(2x-1)(x-1)$ Test numbers in between those zero values to determine if the function is negative or positive (-∞, -1/3] $(+)(-)(-) = (+)$ [-1/3, 1/2] $(-)(-)(-) = (-)$ [1/2, 1] $(-)(+)(-) = (+)$ [1, ∞) $(-)(+)(+) = (-)$ Thus the solution is $[-1/3, 1/2] U [1, ∞ )$
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