Calculus: Early Transcendentals 9th Edition

Published by Cengage Learning
ISBN 10: 1337613924
ISBN 13: 978-1-33761-392-7

Chapter 7 - Section 7.4 - Integration of Rational Functions by Partial Fractions. - 7.4 Exercises - Page 515: 49

Answer

$4\ln \left| {\sqrt x - 2} \right| - 2\ln \left| {\sqrt x - 1} \right| + C$

Work Step by Step

$$\eqalign{ & \int {\frac{1}{{x - 3\sqrt x + 2}}} dx \cr & {\text{Substitute }}x = {u^2},{\text{ then }}dx = 2udu \cr & = \int {\frac{1}{{{u^2} - 3\sqrt {{u^2}} + 2}}\left( {2u} \right)} du \cr & = \int {\frac{{2u}}{{{u^2} - 3u + 2}}} du \cr & {\text{Decompose the integrand into partial fractions}} \cr & \frac{{2u}}{{{u^2} - 3u + 2}} = \frac{{2u}}{{\left( {u - 2} \right)\left( {u - 1} \right)}} = \frac{A}{{u - 2}} + \frac{B}{{u - 1}} \cr & {\text{Multiply both sides by the least common denominator}} \cr & 2u = A\left( {u - 1} \right) + B\left( {u - 2} \right) \cr & u = 2 \to A = 4 \cr & u = 1 \to B = - 2 \cr & \frac{{2u}}{{\left( {u - 2} \right)\left( {u - 1} \right)}} = \frac{4}{{u - 2}} - \frac{2}{{u - 1}} \cr & \int {\frac{{2u}}{{{u^2} - 3u + 2}}} du = \int {\left( {\frac{4}{{u - 2}} - \frac{2}{{u - 1}}} \right)} du \cr & {\text{Integrating}} \cr & = 4\ln \left| {u - 2} \right| - 2\ln \left| {u - 1} \right| + C \cr & {\text{Write in terms of }}x,{\text{ }}x = {u^2} \to u = \sqrt x \cr & = 4\ln \left| {\sqrt x - 2} \right| - 2\ln \left| {\sqrt x - 1} \right| + C \cr} $$
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