Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 6 - Section 6.2 - Adding and Subtracting Rational Expressions - Exercise Set - Page 428: 62

Answer

$\frac{x+4}{x(x+2)}$.

Work Step by Step

The given expression is $=\frac{1}{x}+\frac{4}{x^2-4}-\frac{2}{x^2-2x}$ First denominator $=x$. Second denominator $=x^2-4$. Use the algebraic identity $a^2-b^2=(a+b)(a-b)$. $=x^2-(2)^2$ $=(x+2)(x-2)$ Third denominator $=x^2-2x$. Factor $=x(x-2)$. Substitute all factors into the given expression. $=\frac{1}{x}+\frac{4}{(x+2)(x-2)}-\frac{2}{x(x-2)}$ The LCM of all the denominators is $=x(x+2)(x-2)$. Multiply all fractions to make denominators equal. $=\frac{1}{x}\times \frac{(x+2)(x-2)}{(x+2)(x-2)}+\frac{4}{(x+2)(x-2)}\times \frac{x}{x}-\frac{2}{x(x-2)}\times \frac{(x+2)}{(x+2)}$ Simplify. $=\frac{(x+2)(x-2)}{x(x+2)(x-2)}+\frac{4x}{x(x+2)(x-2)}-\frac{2(x+2)}{x(x+2)(x-2)}$ $=\frac{(x+2)(x-2)+4x-2(x+2)}{x(x+2)(x-2)}$ $=\frac{x^2-4+4x-2x-4}{x(x+2)(x-2)}$ Simplify. $=\frac{x^2+2x-8}{x(x+2)(x-2)}$ Factor the numerator $=x^2+2x-8$ $=x^2+4x-2x-8$ $=(x^2+4x)+(-2x-8)$ $=x(x+4)-2(x+4)$ $=(x+4)(x-2)$ Substitute the factor. $=\frac{(x+4)(x-2)}{x(x+2)(x-2)}$ Cancel common terms. $=\frac{x+4}{x(x+2)}$.
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