Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Appendix B - Review of Partial Fractions - Exercises for B - Problems - Page 803: 3

Answer

\[\frac{x+1}{(x - 3)(x + 2)}=\frac{4}{5(x-3)}+\frac{1}{5(x+2)}\]

Work Step by Step

In this case the general form of the partial fraction decomposition is \[\frac{x+1}{(x - 3)(x + 2)}=\frac{A}{x-3}+\frac{B}{x+2}\;\;\;...(*)\] \[\Rightarrow x+1=A(x+2)+B(x-3)\] \[\Rightarrow x+1=(A+B)x+(2A-3B)\] Comparing like coefficients $A+B=1$ _____(1) $2A-3B=1$ ____(2) Multiply equation (1) by 3 then add to equation (2) $\Rightarrow 5A=4\Rightarrow A=\frac{4}{5}$ From (1) $\Rightarrow B=\frac{1}{5}$ From (*) \[\frac{x+1}{(x - 3)(x + 2)}=\frac{4}{5(x-3)}+\frac{1}{5(x+2)}\] Hence, $\frac{x+1}{(x - 3)(x + 2)}=\frac{4}{5(x-3)}+\frac{1}{5(x+2)}$.
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