Introductory Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-805-X
ISBN 13: 978-0-13417-805-9

Chapter 7 - Section 7.3 - Adding and Subtracting Rational Expressions with the Same Denominator - Exercise Set - Page 507: 72

Answer

$\displaystyle \frac{y^{2}-9y-8}{(y-2)(y-3)}$

Work Step by Step

The third term can be rewritten as $\displaystyle \frac{(y+5)(2y+1)}{[-(y-3)][-(y-2)]}=\frac{(y+5)(2y+1)}{(y-3)(y-2)}$ So, we have $=\displaystyle \frac{(y+1)(2y-1)}{(y-2)(y-3)}+\frac{(y+2)(y-1)}{(y-2)(y-3)}-\frac{(y+5)(2y+1)}{(y-3)(y-2)}$ To add/subtract rational expressions with the same denominator, add/subtract numerators and place the sum/difference over the common denominator. $= \displaystyle \frac{(y+1)(2y-1)+(y+2)(y-1)-(y+5)(2y+1)}{(y-2)(y-3)}$ $= \displaystyle \frac{(2y^{2}-y+2y-1)+(y^{2}-y+2y-2)-(2y^{2}+y+10y+5)}{(y-2)(y-3)}$ $= \displaystyle \frac{2y^{2}+y-1+y^{2}-y+2y-2-2y^{2}-11y-5}{(y-2)(y-3)}$ = $\displaystyle \frac{y^{2}-9y-8}{(y-2)(y-3)}$ ... factoring $x^{2}+bx+c,$ we search for factors of $c$ whose sum is $b$ ... no integer factors of $-8$ whose sum is $-9$ exist ... the numerator can not be factored, we leave it as it is.
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