Thomas' Calculus 13th Edition

Published by Pearson
ISBN 10: 0-32187-896-5
ISBN 13: 978-0-32187-896-0

Chapter 8: Techniques of Integration - Section 8.5 - Integration of Rational Functions by Partial Fractions - Exercises 8.5 - Page 475: 2

Answer

$$\frac{3}{{x - 2}} + \frac{2}{{x - 1}}$$

Work Step by Step

$$\eqalign{ & \frac{{5x - 7}}{{{x^2} - 3x + 2}} \cr & {\text{Factoring the denominator}} \cr & \frac{{5x - 7}}{{\left( {x - 2} \right)\left( {x - 1} \right)}} \cr & {\text{The partial fraction decomposition has the form}} \cr & \frac{{5x - 7}}{{\left( {x - 2} \right)\left( {x - 1} \right)}} = \frac{A}{{x - 2}} + \frac{B}{{x - 1}}\,\,\,\left( {\bf{1}} \right) \cr & \cr & {\text{Find the values of the coefficients }}A,B{\text{; we clear fractions to obtain}} \cr & 5x - 7 = A\left( {x - 1} \right) + B\left( {x - 2} \right) \cr & \,\,\,\,\,{\text{set }}x = 2 \cr & 5\left( 2 \right) - 7 = A\left( {2 - 1} \right) + B\left( {2 - 2} \right) \cr & 3 = A \cr & \,\,\,\,\,{\text{set }}x = 1 \cr & 5\left( 1 \right) - 7 = A\left( {1 - 1} \right) + B\left( {1 - 2} \right) \cr & - 2 = B\left( { - 1} \right) \cr & B = 2 \cr & {\text{Then substituting }}A{\text{ and }}B{\text{ into the equation }}\left( {\bf{1}} \right) \cr & \frac{{5x - 7}}{{\left( {x - 2} \right)\left( {x - 1} \right)}} = \frac{3}{{x - 2}} + \frac{2}{{x - 1}} \cr} $$
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