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: 40

Answer

$$ - \frac{2}{{2x}} - \frac{2}{{{x^2}}} + \frac{2}{{2\left( {x - 2} \right)}}$$

Work Step by Step

$$\eqalign{ & \frac{{2x + 4}}{{{x^3} - 2{x^2}}} \cr & {\text{Factor the denominator}} \cr & \frac{{2x + 4}}{{{x^3} - 2{x^2}}} = \frac{{2x + 4}}{{{x^2}\left( {x - 2} \right)}} \cr & {\text{Decompose }}\frac{{2x + 4}}{{{x^2}\left( {x - 2} \right)}}{\text{ into partial fractions}} \cr & \frac{{2x + 4}}{{{x^2}\left( {x - 2} \right)}} = \frac{A}{x} + \frac{B}{{{x^2}}} + \frac{C}{{x - 2}} \cr & \cr & {\text{Multiply each side by }}x\left( {x + 2} \right)\left( {x - 1} \right) \cr & 2x + 4 = Ax\left( {x - 2} \right) + B\left( {x - 2} \right) + C{x^2} \cr & 2x + 4 = A{x^2} - 2Ax + Bx - 2B + C{x^2} \cr & 2x + 4 = A{x^2} + C{x^2} + \left( { - 2A + B} \right)x - 2B \cr & {\text{Equating the coefficients}} \cr & A + C = 0 \cr & - 2A + B = 2 \cr & - 2B = 4 \cr & {\text{Solving the system of equations we obtain}} \cr & A = - 2,\,\,\,B = - 2,\,\,\,C = 2 \cr & {\text{Use }}A,{\text{ }}B\,\,{\text{ and }}C{\text{ to find the partial fraction decomposition}} \cr & \frac{{2x + 4}}{{{x^2}\left( {x - 2} \right)}} = - \frac{2}{{2x}} - \frac{2}{{{x^2}}} + \frac{2}{{2\left( {x - 2} \right)}} \cr} $$
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