Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 7 - Principles Of Integral Evaluation - 7.5 Integrating Rational Functions By Partial Fractions - Exercises Set 7.5 - Page 521: 12

Answer

$$\ln \left| {x - 3} \right| + \frac{2}{3}\ln \left| {3x + 1} \right| + C$$

Work Step by Step

$$\eqalign{ & \int {\frac{{5x - 5}}{{3{x^2} - 8x - 3}}} dx \cr & {\text{Decomposing the integrand into partial fractions}} \cr & {\text{Factor the denominator}} \cr & \frac{{5x - 5}}{{3{x^2} - 8x - 3}} = \frac{{5x - 5}}{{\left( {x - 3} \right)\left( {3x + 1} \right)}} \cr & {\text{The form of the partial fraction decomposition is}} \cr & \frac{{5x - 5}}{{\left( {x - 3} \right)\left( {3x + 1} \right)}} = \frac{A}{{x - 3}} + \frac{B}{{3x + 1}} \cr & {\text{Multiplying the equation by }}\left( {x - 3} \right)\left( {3x + 1} \right){\text{, we have}} \cr & 5x - 5 = A\left( {3x + 1} \right) + B\left( {x - 3} \right) \cr & {\text{if we set }}x = 3 \cr & 5\left( 3 \right) - 5 = A\left( {3\left( 3 \right) + 1} \right) + B\left( 0 \right) \cr & 10 = A\left( {10} \right) \cr & A = 1 \cr & {\text{if we set }}x = - 1/3 \cr & 5\left( { - 1/3} \right) - 5 = A\left( 0 \right) + B\left( { - \frac{1}{3} - 3} \right) \cr & B = 2 \cr & {\text{then}} \cr & \frac{{5x - 5}}{{\left( {x - 3} \right)\left( {3x + 1} \right)}} = \frac{1}{{x - 3}} + \frac{2}{{3x + 1}} \cr & \cr & \int {\frac{{5x - 5}}{{3{x^2} - 8x - 3}}} dx = \int {\left( {\frac{1}{{x - 3}} + \frac{2}{{3x + 1}}} \right)dx} \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \int {\frac{1}{{x - 3}}dx} + \frac{2}{3}\int {\frac{3}{{3x + 1}}} dx \cr & {\text{integrating}} \cr & = \ln \left| {x - 3} \right| + \frac{2}{3}\ln \left| {3x + 1} \right| + C \cr} $$
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