Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 8 - Integration Techniques, L'Hopital's Rule, and Improper Integrals - 8.5 Exercises - Page 549: 12

Answer

$$\frac{2}{5}\ln \left| x \right| + \frac{3}{5}\ln \left| {x + 5} \right| + C$$

Work Step by Step

$$\eqalign{ & \int {\frac{{x + 2}}{{{x^2} + 5x}}} dx \cr & {\text{Decompose the integrand into partial fractions}} \cr & \frac{{x + 2}}{{{x^2} + 5x}} = \frac{{x + 2}}{{x\left( {x + 5} \right)}} \cr & \frac{{x + 2}}{{x\left( {x + 5} \right)}} = \frac{A}{x} + \frac{B}{{x + 5}} \cr & x + 2 = A\left( {x + 5} \right) + Bx \cr & {\text{For }}x = 0 \cr & 2 = A\left( 5 \right) + B\left( 0 \right) \to A = \frac{2}{5} \cr & {\text{For }}x = - 5 \cr & - 5 + 2 = A\left( 0 \right) + B\left( { - 5} \right) \to B = \frac{3}{5} \cr & \frac{{x + 2}}{{x\left( {x + 5} \right)}} = \frac{{2/5}}{x} + \frac{{3/5}}{{x + 5}} \cr & \int {\frac{{x + 2}}{{{x^2} + 5x}}} dx = \int {\left( {\frac{{2/5}}{x} + \frac{{3/5}}{{x + 5}}} \right)} dx \cr & {\text{Integrate}} \cr & {\text{ = }}\frac{2}{5}\ln \left| x \right| + \frac{3}{5}\ln \left| {x + 5} \right| + C \cr} $$
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