Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Appendix A - Review - A.5 Rational Expressions - A.5 Assess Your Understanding - Page A41: 20

Answer

$\dfrac{3}{x-2}, x\ne -2, 0, 2$

Work Step by Step

The initial restrictions is $x\ne0$. Use the rule $\frac{a}{b}\div \frac{c}{d} = \frac{a}{b} \cdot \frac{d}{c}$ to obtain: $\dfrac{x-2}{4x} \cdot \dfrac{12x}{x^2-4x+4}$ $=\dfrac{x-2}{4x} \cdot \dfrac{12x}{x^2-2(x)(2)+2^2}$ Factor each polynomial completely. Use special formula $a^2-2ab+b^2=(a-b)^2$ to obtain: $=\dfrac{x-2}{4x} \cdot \dfrac{3\cdot 4x}{(x-2)^2}$ $=\dfrac{x-2}{4x} \cdot \dfrac{3\cdot 4x}{(x-2)(x-2)}$ This yields an additional restriction $x\ne \pm2$. Cancel the common factor $x-2$ to obtain:. $=\dfrac{3}{x-2}, x\ne -2, 0, 2$ Hence, the lowest term is: $\dfrac{3}{x-2}, \space x\ne -2, 0, 2$
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