Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 9 - Systems and Matrices - 9.4 Partial Fractions - 9.4 Exercises - Page 895: 22

Answer

$$1 + \frac{1}{x} + \frac{5}{{x - 2}} - \frac{3}{{x - 1}}$$

Work Step by Step

$$\eqalign{ & \frac{{{x^3} + 2}}{{{x^3} - 3{x^2} + 2x}} \cr & {\text{Use the long division}} \cr & \frac{{{x^3} + 2}}{{{x^3} - 3{x^2} + 2x}} = 1 + \frac{{3{x^2} - 2x + 2}}{{{x^3} - 3{x^2} + 2x}} \cr & {\text{Decompose }}\frac{{3{x^2} - 2x + 2}}{{{x^3} - 3{x^2} + 2x}} \cr & \frac{{3{x^2} - 2x + 2}}{{{x^3} - 3{x^2} + 2x}} = \frac{{3{x^2} - 2x + 2}}{{x\left( {{x^2} - 3x + 2} \right)}} = \frac{{3{x^2} - 2x + 2}}{{x\left( {x - 2} \right)\left( {x - 1} \right)}} \cr & {\text{The partial fraction decomposition is }} \cr & \frac{{3{x^2} - 2x + 2}}{{x\left( {x - 2} \right)\left( {x - 1} \right)}} = \frac{A}{x} + \frac{B}{{x - 2}} + \frac{C}{{x - 1}} \cr & {\text{Multiply each side by }}x\left( {x - 2} \right)\left( {x - 1} \right) \cr & 3{x^2} - 2x + 2 = A\left( {x - 2} \right)\left( {x - 1} \right) + Bx\left( {x - 1} \right) + Cx\left( {x - 2} \right)\,\,\,\,\,\,\,\,\,\,\left( 1 \right) \cr & \cr & {\text{Let }}x = 0{\text{ into the equation }}\left( 1 \right) \cr & 2 = A\left( { - 2} \right)\left( { - 1} \right) + B\left( 0 \right) + C\left( 0 \right)\, \cr & A = 1 \cr & \cr & {\text{Let }}x = 2{\text{ into the equation }}\left( 1 \right) \cr & 10 = A\left( 0 \right) + 2B\left( {2 - 1} \right) + C\left( 0 \right)\,\,\,\,\,\,\,\,\,\,\left( 1 \right) \cr & B = 5 \cr & \cr & {\text{Let }}x = 1{\text{ into the equation }}\left( 1 \right) \cr & 3 = A\left( 0 \right) + B\left( 0 \right) + C\left( {1 - 2} \right)\,\,\,\,\,\,\,\,\,\,\left( 1 \right) \cr & C = - 3 \cr & \cr & {\text{Use }}A,{\text{ }}B{\text{ and }}C{\text{ to find the partial fraction decomposition}} \cr & \frac{{3{x^2} - 2x + 2}}{{x\left( {x - 2} \right)\left( {x - 1} \right)}} = \frac{1}{x} + \frac{5}{{x - 2}} - \frac{3}{{x - 1}} \cr & \frac{{{x^3} + 2}}{{{x^3} - 3{x^2} + 2x}} = 1 + \frac{1}{x} + \frac{5}{{x - 2}} - \frac{3}{{x - 1}} \cr} $$
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