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 427: 33

Answer

$\displaystyle \frac{3x-4}{(x+2)(x-3)}$

Work Step by Step

1. Find the LCD . 1st denominator = $(x+2)(x-1)$ 2nd denominator = $(x-3)(x-1)$ List factors of the 1st denominator. From each next denominator, add only those factors that do not yet appear in the list. LCD = $(x+2)(x-1)(x-3)$ 2. Rewrite each rational expression with the the LCDas the denominator $\displaystyle \frac{3x(x-3)}{(x+2)(x-1)(x-3)}+\frac{2(x+2)}{(x-3)(x-1)(x+2)}$ 3. Add or subtract numerators, placing the resulting expression over the LCD. $= \displaystyle \frac{3x(x-3)+2(x+2)}{(x+2)(x-1)(x-3)}$ 4. If possible, simplify. $= \displaystyle \frac{3x^{2}-9x+2x+4}{(x+2)(x-1)(x-3)} $ $= \displaystyle \frac{3x^{2}-7x+4}{(x+2)(x-1)(x-3)}$ The numerator is of the form $ax^{2}+bx+c.$ To factor, find factors of $ac$ whose sum is $b.$ If successful, rewrite $bx$ and factor in pairs. $3x^{2}-7x+4$=$3x^{2}-3x-4x+4$ =$3x(x-1)-4(x-1)=(x-1)(3x-4)$ = $\displaystyle \frac{(x-1)(3x-4)}{(x+2)(x-1)(x-3)}\qquad$... cancel the common factor = $\displaystyle \frac{3x-4}{(x+2)(x-3)}$
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