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: 18

Answer

$$ - \frac{2}{{x + 1}} + \frac{2}{{x + 2}} + \frac{4}{{{{\left( {x + 2} \right)}^2}}}$$

Work Step by Step

$$\eqalign{ & \frac{{2x}}{{\left( {x + 1} \right){{\left( {x + 2} \right)}^2}}} \cr & {\text{The partial fraction decomposition is }} \cr & \frac{{2x}}{{\left( {x + 1} \right){{\left( {x + 2} \right)}^2}}} = \frac{A}{{x + 1}} + \frac{B}{{x + 2}} + \frac{C}{{{{\left( {x + 2} \right)}^2}}} \cr & {\text{Multiply each side by }}\left( {x + 1} \right){\left( {x + 2} \right)^2} \cr & 2x = A{\left( {x + 2} \right)^2} + B\left( {x + 1} \right)\left( {x + 2} \right) + C\left( {x + 1} \right)\,\,\,\,\,\,\,\,\,\,\left( 1 \right) \cr & \cr & {\text{Let }}x = - 1{\text{ into the equation }}\left( 1 \right) \cr & 2\left( { - 1} \right) = A{\left( { - 1 + 2} \right)^2} + B\left( 0 \right) + C\left( 0 \right)\, \cr & - 2 = A \cr & A = - 2 \cr & \cr & {\text{Let }}x = - 2{\text{ into the equation }}\left( 1 \right) \cr & 2\left( { - 2} \right) = A{\left( 0 \right)^2} + B\left( 0 \right) + C\left( { - 2 + 1} \right)\,\, \cr & - 4 = C\left( { - 1} \right)\,\, \cr & C = 4 \cr & \cr & {\text{Let }}x = 0,\,\,C = 4{\text{ and }}A = - 2{\text{ into the equation }}\left( 1 \right) \cr & 2\left( 0 \right) = - 2{\left( {0 + 2} \right)^2} + B\left( {0 + 1} \right)\left( {0 + 2} \right) + 4\left( {0 + 1} \right)\,\, \cr & 0 = - 2\left( 4 \right) + B\left( 1 \right)\left( 2 \right) + 4\left( 1 \right)\,\, \cr & B = 2 \cr & \cr & {\text{Use }}A,{\text{ }}B{\text{ and }}C{\text{ to find the partial fraction decomposition}} \cr & \frac{{2x}}{{\left( {x + 1} \right){{\left( {x + 2} \right)}^2}}} = - \frac{2}{{x + 1}} + \frac{2}{{x + 2}} + \frac{4}{{{{\left( {x + 2} \right)}^2}}} \cr} $$
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