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 A42: 27

Answer

$\dfrac{5x}{(x-6)(x-1)(x+4)}$.

Work Step by Step

Factor $x^2-7x+6$: Rewrite $-7x$ as $-6x-1x$. $=x^2-6x-1x+6$ Group the terms. $=(x^2-6x)+(-1x+6)$ Factor each group. $=x(x-6)-1(x-6)$ Factor out $(x-6)$. $=(x-6)(x-1)$ Factor $x^2-2x-24$: Rewrite $-2x$ as $-6x+4x$. $=x^2-6x+4x-24$ Group the terms. $=(x^2-6x)+(4x-24)$ Factor each group. $=x(x-6)+4(x-6)$ Factor out $(x-6)$. $=(x-6)(x+4)$ Thus, the given expression is eqivalent to: $\dfrac{x}{(x-6)(x-1)}-\dfrac{x}{(x-6)(x+4)}$ The LCD is $(x-6)(x-1)(x+4)$. Multiply numerators and denominators to form equal denominators. $=\dfrac{x}{(x-6)(x-1)}\cdot \dfrac{x+4}{x+4}-\dfrac{x}{(x-6)(x+4)}\cdot \dfrac{x-1}{x-1}$ $=\dfrac{x(x+4)}{(x-6)(x-1)(x+4)}-\dfrac{x(x-1)}{(x-6)(x-1)(x+4)}$ Add numerators and retain the denominator. $=\dfrac{x(x+4)-x(x-1)}{(x-6)(x-1)(x+4)}$ Use distributive property. $=\dfrac{x^2+4x-x^2+x}{(x-6)(x-1)(x+4)}$ Simplify by combining like terms: $=\dfrac{5x}{(x-6)(x-1)(x+4)}$
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