Calculus: Early Transcendentals (2nd Edition)

Published by Pearson
ISBN 10: 0321947347
ISBN 13: 978-0-32194-734-5

Chapter 7 - Integration Techniques - 7.5 Partial Fractions - 7.5 Exercises - Page 549: 28

Answer

$$9\ln \left| {x - 6} \right| + 7\ln \left| {x + 2} \right| + \frac{8}{{x + 2}} + C$$

Work Step by Step

$$\eqalign{ & \int {\frac{{16{x^2}}}{{\left( {x - 6} \right){{\left( {x + 2} \right)}^2}}}dx} \cr & {\text{integrand }} \cr & = \frac{{16{x^2}}}{{\left( {x - 6} \right){{\left( {x + 2} \right)}^2}}} \cr & {\text{partial fractions}} \cr & \frac{{16{x^2}}}{{\left( {x - 6} \right){{\left( {x + 2} \right)}^2}}} = \frac{A}{{x - 6}} + \frac{B}{{x + 2}} + \frac{C}{{{{\left( {x + 2} \right)}^2}}} \cr & 16{x^2} = A{\left( {x + 2} \right)^2} + B\left( {x - 6} \right)\left( {x + 2} \right) + C\left( {x - 6} \right) \cr & {\text{multiplying}} \cr & 16{x^2} = A\left( {{x^2} + 4x + 4} \right) + B\left( {{x^2} - 4x - 12} \right) + C\left( {x - 6} \right) \cr & 16{x^2} = A{x^2} + 4Ax + 4A + B{x^2} - 4Bx - 12B + Cx - 6C \cr & 16{x^2} = \left( {A{x^2} + B{x^2}} \right) + \left( {4Ax - 4Bx + Cx} \right) + \left( {4A - 12B - 6C} \right) \cr & {\text{by equating the coefficients}} \cr & {x^2}:{\text{ }}A + B = 16 \cr & x:{\text{ }}4A - 4B + C = 0 \cr & {x^0}:{\text{ }}4A - 12B - 6C = 0 \cr & {\text{Solving these equations}} \cr & A = 9 \cr & B = 7 \cr & C = - 8 \cr & {\text{substituting constants}} \cr & \frac{{16{x^2}}}{{\left( {x - 6} \right){{\left( {x + 2} \right)}^2}}} = \frac{9}{{x - 6}} + \frac{7}{{x + 2}} - \frac{8}{{{{\left( {x + 2} \right)}^2}}} \cr & \int {\frac{{16{x^2}}}{{\left( {x - 6} \right){{\left( {x + 2} \right)}^2}}}dx} = \int {\left( {\frac{9}{{x - 6}} + \frac{7}{{x + 2}} - \frac{8}{{{{\left( {x + 2} \right)}^2}}}} \right)dx} \cr & {\text{integrating}} \cr & = 9\ln \left| {x - 6} \right| + 7\ln \left| {x + 2} \right| + \frac{8}{{x + 2}} + C \cr} $$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.