College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 5 - Summary, Review, and Test - Review Exercises - Page 585: 16

Answer

$\dfrac{x}{(x-3)(x+2)}=\dfrac{3}{5(x-3)}+\dfrac{2}{5(x+2)}$

Work Step by Step

We are given the fraction: $\dfrac{x}{(x-3)(x+2)}$ The denominator is factored, therefore we can write the partial fraction decomposition: $\dfrac{x}{(x-3)(x+2)}=\dfrac{A}{x-3}+\dfrac{B}{x+2}$ Multiply each terms by the least common denominator $(x-3)(x+2)$: $(x-3)(x+2)\cdot\dfrac{x}{(x-3)(x+2)}=(x-3)(x+2)\cdot\dfrac{A}{x-3}+(x-3)(x+2)\cdot\dfrac{B}{x+2}$ $x=A(x+2)+B(x-3)$ $x=Ax+2A+Bx-3B$ $x=(A+B)x+(2A-3B)$ Identify the coefficients: $\begin{cases} A+B=1\\ 2A-3B=0 \end{cases}$ Solve the system: $\begin{cases} -2A-2B==-2\\ 2A-3B=0 \end{cases}$ $-2A-2B+2A-3B=-2+0$ $-5B=-2$ $B=\dfrac{2}{5}$ $A+B=1$ $A+\dfrac{2}{5}=1$ $A=1-\dfrac{2}{5}$ $A=\dfrac{3}{5}$ The partial fraction decomposition is: $\dfrac{x}{(x-3)(x+2)}=\dfrac{\dfrac{3}{5}}{x-3}+\dfrac{\dfrac{2}{5}}{x+2}$ $\dfrac{x}{(x-3)(x+2)}=\dfrac{3}{5(x-3)}+\dfrac{2}{5(x+2)}$
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