College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 5, Systems of Equations and Inequalities - Chapter 5 Review - Exercises - Page 479: 34

Answer

$\frac{5x^2-3x+10}{(x^2+2)(x-1)(x+1)}=\frac{2}{x-1}+\frac{-3}{x+1}+\frac{x}{x^2+2}$

Work Step by Step

$\frac{5x^2-3x+10}{x^4+x^2-2}$, factorising $x^4+x^2-2=(x^2-1)(x^2+2)=(x-1)(x+1)(x^2+2)$, thus, $\frac{5x^2-3x+10}{(x-1)(x+1)(x^2+2)}=\frac{A}{x-1}+\frac{B}{x+1}+\frac{Cx+D}{x^2+2}$, $A(x+1)(x^2+2)+B(x-1)(x^2+2)+(Cx+D)(x+1)(x-1)$, $(A+B+C)x^3+(A-B+D)x^2+(2A+2B-C)x+(2A-2B-D)=5x^2-3x+10$, $\begin{cases} A+B+C=0\\ A-B+D=5\\ 2A+2B-C=-3\\ 2A-2B-D=10 \end{cases}$, Adding Equation 1 and Equation 2. $\begin{cases} A+B+C=0\\ A-B+D=5\\ -- -- -- --\\ 2A+C+D=5 \end{cases}$ Adding Equation 3 and Equation 4. $\begin{cases} 2A+2B-C=-3\\ 2A-2B-D=10\\ -- -- -- --\\ 4A-C-D=7 \end{cases}$ $\begin{cases} 2A+C+D=5\\ 4A-C-D=7\\ -- -- -- -- -- -\\ 6A=12 \end{cases}$ thus, $A=2$, substituting back into the Equation 1 $B+C=-2$ and Equation 3 $2B-C=-7$. Adding Equation 1 and Equation 3. $\begin{cases} B+C=-2\\ 2B-C=-7\\ -- -- -- --\\ 3B=-9 \end{cases}$ thus, $B=-3$, substituting into the Equation, $-3+C=-2, C=1$ and $5+D=5, D=0$. Therefore, $\frac{5x^2-3x+10}{(x^2+2)(x-1)(x+1)}=\frac{2}{x-1}+\frac{-3}{x+1}+\frac{x}{x^2+2}$
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