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: 25

Answer

$\dfrac{x^2+2x+7}{x(x-1)^2}=\dfrac{7}{x}-\dfrac{6}{x-1}+\dfrac{10}{(x-1)^2}$

Work Step by Step

We are given the fraction: $\dfrac{x^2+2x+7}{x(x-1)^2}$ As the denominator is already factored, we can write the partial fraction decomposition: $\dfrac{x^2+2x+7}{x(x-1)^2}=\dfrac{A}{x}+\dfrac{B}{x-1}+\dfrac{C}{(x-1)^2}$ Multiply all terms by the least common denominator $x(x-1)^2$: $x(x-1)^2\cdot\dfrac{x^2+2x+7}{x(x-1)^2}=x(x-1)^2\cdot\dfrac{A}{x}+x(x-1)^2\cdot\dfrac{B}{x-1}+x(x-1)^2\cdot\dfrac{C}{(x-1)^2}$ $x^2+2x+7=A(x-1)^2+Bx(x-1)+Cx$ $x^2+2x+7=Ax^2-2Ax+A+Bx^2-Bx+Cx$ $x^2+2x+7=(A+B)x^2+(-2A-B+C)x+A$ Identify the coefficients and build the system of equations: $\begin{cases} A+B=1\\ -2A-B+C=2\\ A=7 \end{cases}$ Solve the system: $A=7$ $7+B=1$ $B=-6$ $-2(7)-(-6)+C=2$ $-14+6+C=2$ $-8+C=2$ $C=10$ The partial fraction decomposition is: $\dfrac{x^2+2x+7}{x(x-1)^2}=\dfrac{7}{x}-\dfrac{6}{x-1}+\dfrac{10}{(x-1)^2}$
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