Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 9 - Systems and Matrices - 9.4 Partial Fractions - 9.4 Exercises - Page 895: 21

Answer

$\dfrac{1}{9}-\dfrac{1}{x}+\dfrac{25}{18(3x+2)}+\dfrac{29}{18(3x-2)} $

Work Step by Step

We will write the partial decomposition as: $\dfrac{1}{9}+\dfrac{\dfrac{4}{9}x+4}{x(3x+2) (3x-2)}=\dfrac{1}{9}+\dfrac{A}{x}+\dfrac{B}{3x+2}+\dfrac{C}{3x-2} ~~~~(a)$ This implies that $\dfrac{4}{9}x+4=A(3x+2)(3x-2)+Bx(3x-2)+Cx(3x-2)$ Plug $x=0, -1$ to obtain: $4=-4A \implies A=-1$ After solving these equations, we get: $B=\dfrac{25}{18} $ and $C=\dfrac{29}{18}$ So, the equation (a) becomes: $\dfrac{1}{9}+ \dfrac{\dfrac{4}{9}x+4}{x(3x+2) (3x-2)}=\dfrac{1}{9}-\dfrac{1}{x}+\dfrac{25}{18(3x+2)}+\dfrac{29}{18(3x-2)} $
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