College Algebra (6th Edition)

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

Chapter 5 - Systems of Equations and Inequalities - Exercise Set 5.3 - Page 550: 40

Answer

$\dfrac{3x^3-6x^2+7x-2}{(x^2-2x+2)^2}=\dfrac{3x}{x^2-2x+2}+\dfrac{x-2}{(x^2-2x+2)^2}$

Work Step by Step

We are given the fraction: $\dfrac{3x^3-6x^2+7x-2}{(x^2-2x+2)^2}$ As the denominator is factored, we can write the partial fraction decomposition: $\dfrac{3x^3-6x^2+7x-2}{(x^2-2x+2)^2}=\dfrac{Ax+B}{x^2-2x+2}+\dfrac{Cx+D}{(x^2-2x+2)^2}$ Multiply all terms by the least common denominator $(x^2-2x+2)^2$: $(x^2-2x+2)^2\cdot\dfrac{3x^3-6x^2+7x-2}{(x^2-2x+2)^2}=(x^2-2x+2)^2\cdot\dfrac{Ax+B}{x^2-2x+2}+(x^2-2x+2)^2\cdot\dfrac{Cx+D}{(x^2-2x+2)^2}$ $3x^3-6x^2+7x-2=(Ax+B)(x^2-2x+2)+(Cx+D)$ $3x^3-6x^2+7x-2=Ax^3-2Ax^2+2Ax+Bx^2-2Bx+2B+Cx+D$ $3x^3-6x^2+7x-2=Ax^3+(-2A+B)x^2+(2A-2B+C)x+(2B+D)$ Identify the coefficients and build the system of equations: $\begin{cases} A=3\\ -2A+B=-6\\ 2A-2B+C=7\\ 2B+D=-2 \end{cases}$ Solve the system: $A=3$ $\begin{cases} -2(3)+B=-6\\ 2(3)-2B+C=7\\ 2B+D=-2 \end{cases}$ $\begin{cases} -6+B=-6\\ 6-2B+C=7\\ 2B+D=-2 \end{cases}$ $B=0$ $\begin{cases} 6-2(0)+C=7\\ 2(0)+D=-2 \end{cases}$ $\begin{cases} 6+C=7\\ D=-2 \end{cases}$ $C=1$ $D=-2$ The partial fraction decomposition is: $\dfrac{3x^3-6x^2+7x-2}{(x^2-2x+2)^2}=\dfrac{3x}{x^2-2x+2}+\dfrac{x-2}{(x^2-2x+2)^2}$
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