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: 33

Answer

$\frac{-10x^2+27x-14}{(x-1)^3(x+2)}=\frac{4}{x+2}+\frac{-4}{x-1}+\frac{2}{(x-1)^2}+\frac{1}{(x-1)^3}$,

Work Step by Step

$\frac{-10x^2+27x-14}{(x-1)^3(x+2)}=\frac{A}{x+2}+\frac{B}{x-1}+\frac{C}{(x-1)^2}+\frac{D}{(x-1)^3}$, $A(x-1)^3+B(x-1)^2(x+2)+C(x-1)(x+2)+D(x+2)$, $A(x^3-3x^2+3x-1)+B(x^3-3x+2)+C(x^2+x-2)+D(x+2)$, $(A+B)x^3+(-3A+C)x^2+(3A-3B+C+D)x+(-A+2B-2C+2D)$, $\begin{cases} & A & +B=0\\ & -3A & +C = -10\\ 3A & -3B & +C +D=27\\ -A & +2B & -2C +2D= -14 \end{cases}$ Multiplying Equation $4$ by $3$ and adding it to Equation $3$. $\begin{cases} -3A +6B -6C +6D=-42\\ 3A -3B +C +D=27\\ -- -- -- -- -- -- -- --\\ 0A +3B -5C +7D=-15 \end{cases}$ Adding Equation $2$ and Equation $3$. $\begin{cases} & -3A +C=-10\\ & +3A -3B +C +D=27\\ & -- -- -- -- -- -- -- --\\ & 0A -3B +2C +D=17 \end{cases}$ Multiplying Equation $1$ by $3$ and adding it to Equation $2$. $\begin{cases} & 3A +3B=0\\ & -3A +C=-10\\ & -- -- -- -- --\\ & 0A +3B +C=-10 \end{cases}$ Adding the Addition result of Equation $4$, Equation $3$ and the Addition result of Equation $2$, Equation $3$ $\begin{cases} & 3B -5C +7D=-15\\ & -3B +2C +D=17\\ & -- -- -- -- -- --\\ & -3C +8D=2 \end{cases}$ Adding the Addition result of Equation $1$, Equation $2$ and Equation $2$, Equation $3$. $\begin{cases} & -3B +2C +D=17\\ & 3B +C=-10\\ & -- -- -- -- -- &\\ & 3C +D=7 \end{cases}$ Adding the Addition result... $\begin{cases} & -3C+8D=2\\ & 3C+D=7\\ & -- -- -- --\\ & +9D=9 \end{cases}$ thus, $D=1$, Substituting back into the Equation, $3C+1=7, C=2$. Substituting back into the Equation, $3B+2=-10, B=-4$. Substituting back into the Equation, $A-4=0, A=4$. Therefore, $\frac{-10x^2+27x-14}{(x-1)^3(x+2)}=\frac{4}{x+2}+\frac{-4}{x-1}+\frac{2}{(x-1)^2}+\frac{1}{(x-1)^3}$,
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