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: 45

Answer

$\dfrac{x^4-x^2+2}{x^3-x^2}=x+1-\dfrac{2}{x}-\dfrac{2}{x^2}+\dfrac{2}{x-1}$

Work Step by Step

We are given the fraction: $\dfrac{x^4-x^2+2}{x^3-x^2}$ Because the degree of the numerator is greater than the degree of the denominator, we divide the numerator by the denominator: $\dfrac{x^4-x^2+2}{x^3-x^2}=\dfrac{x(x^3-x^2)+x^3-x^2+2}{x^3-x^2}=\dfrac{x(x^3-x^2)+(x^3-x^2)+2}{x^3-x^2}=\dfrac{(x^3-x^2)(x+1)+2}{x^3-x^2}=x+1+\dfrac{2}{x^3-x^2}$ We will write the partial fraction decomposition for the fraction $\dfrac{2}{x^3-x^2}$. Factor the denominator and write the partial fraction decomposition: $\dfrac{2}{x^3-x^2}=\dfrac{2}{x^2(x-1)}$ Write the partial fraction decomposition: $\dfrac{2}{x^3-x^2}=\dfrac{A}{x}+\dfrac{B}{x^2}+\dfrac{C}{x-1}$ Multiply all terms by the least common denominator $x^2(x-1)$: $x^2(x-1)\cdot\dfrac{2}{x^3-x^2}=x^2(x-1)\cdot\dfrac{A}{x}+x^2(x-1)\cdot\dfrac{B}{x^2}+x^2(x-1)\cdot\dfrac{C}{x-1}$ $2=Ax(x-1)+B(x-1)+Cx^2$ $2=Ax^2-Ax+Bx-B+Cx^2$ $2=(A+C)x^2+(-A+B)x-B$ Identify the coefficients: $\begin{cases} A+C=0\\ -A+B=0\\ -B=2 \end{cases}$ $B=-2$ $-A+B=0$ $-A+(-2)=0$ $A=-2$ $A+C=0$ $-2+C=0$ $C=2$ The partial fraction decomposition is: $\dfrac{2}{x^2(x-1)}=-\dfrac{2}{x}-\dfrac{2}{x^2}+\dfrac{2}{x-1}$ The final result is: $\dfrac{x^4-x^2+2}{x^3-x^2}=x+1-\dfrac{2}{x}-\dfrac{2}{x^2}+\dfrac{2}{x-1}$
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