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: 40

Answer

$(-∞, 0)) U (1, ∞)$

Work Step by Step

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