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: 23

Answer

$(-∞, -3) U (-2/3, 1) U (3, ∞)$

Work Step by Step

$\frac{x^2 + 2x - 3}{3x^2 - 7x - 6} > 0$ Find the zeros of the expressions in the numerator AND the denominator $x^2 + 2x - 3 = 0$ $(x+3) (x-1) = 0$ $x = -3, 1$ $3x^2 - 7x - 6 = 0$ $(3x + 2) (x - 3) = 0$ $x = -2/3, 3$ $\frac{(x+3) (x-1)}{(3x + 2) (x - 3)} \leq 0$ Test numbers in between those zero values to determine if the function is negative or positive $(-∞, -3)$ $\frac{(-)(-)}{(-)(-)} = (+)$ $(-3,-2/3)$ $\frac{(+)(-)}{(-)(-)} = (-)$ $(-2/3, 1)$ $\frac{(+)(-)}{(+)(-)} = (+)$ $(1, 3)$$\frac{(+)(+)}{(+)(-)} = (-)$ $(3, ∞)$ $\frac{(+)(+)}{(+)(+)} = (+)$ Thus the solution is $(-∞, -3) U (-2/3, 1) U (3, ∞)$
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