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 - Section 5.3 - Partial Fractions - 5.3 Exercises - Page 462: 34

Answer

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

Work Step by Step

$\frac{-2x^2+5x-1}{x^4-2x^3+2x-1}$ = factorising $x^4-2x^3+2x-1=(x^2-2x+1)(x^2-1)=(x-1)(x+1)(x-1)(x-1)=(x-1)^3(x+1)$, $\frac{-2x^2+5x-1}{(x+1)(x-1)^3}=\frac{A}{x+1}+\frac{B}{x-1}+\frac{C}{(x-1)^2}+\frac{D}{(x-1)^3}$, $A(x-1)^3+B(x-1)^2(x+1)+C(x-1)(x+1)+D(x+1)$, $A(x^3-3x^2+3x-1)+B(x^3-x^2-x+1)+C(x^2-1)+D(x+1)$, $(A+B)x^3+(-3A-B+C)x^2+(3A-B+D)x+(-A+B-C+D)$, $\begin{cases} & A & +B=0\\ & -3A & -B +C = -2\\ 3A & -B & +D=5\\ -A & +B & -C +D= -1 \end{cases}$ Adding Equation $2$ and Equation $3$. $\begin{cases} -3A -B +C=-2\\ 3A -B +D=5\\ -- -- -- -- -- -- -- --\\ 0A -2B +C +D=3 \end{cases}$ Adding Equation $1$ and Equation $4$. $\begin{cases} & A +B=0\\ & -A +B -C +D=-1\\ & -- -- -- -- -- -- -- --\\ & 0A +2B -C +D=-1 \end{cases}$ Adding the Addition result of Equation $2$, Equation $3$ and the Addition result of Equation $1$, Equation $4$ $\begin{cases} & 2B -C +D=-1\\ & -2B +C +D=3\\ & -- -- -- -- -- --\\ & 0C +2D=2 \end{cases}$ thus, $D=1$, Adding Equation $1$ and Equation $3$. $\begin{cases} & A +B=0\\ & 3A-B=4\\ & -- -- -- -- --\\ & 4A +0B=4 \end{cases}$ thus, $A=1$ Substituting back into the Equation, $1+B=0, B=-1$. Substituting back into the Equation, $-3+1+C=-2, C=0$. Therefore, $\frac{-2x^2+5x-1}{(x-1)^3(x+1)}=\frac{1}{x+2}+\frac{-1}{x-1}+\frac{1}{(x-1)^3}$,
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