Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 10 - Review - Exercises - Page 771: 88

Answer

$\frac{1}{x-2}-\frac{x+1}{x^2+4}$

Work Step by Step

Step 1. Factorize the denominator as: $x^2(x-2)+4(x-2)=(x-2)(x^2+4))$ Step 2. Assume the partial fraction decomposition is: $\frac{A}{x-2}+\frac{Bx+C}{x^2+4}$ Step 3. Combine the rational functions above: $\frac{A(x^2+4)+(Bx+C)(x-2)}{(x-2)(x^2+4)}\frac{(A+B)x^2+(-2B+C)x+(4A-2C)}{x(x-1)^2}$ Step 4. Compare the above function with the original to setup the following system of equations: $\begin{cases} A+B=0\\-2B+C=1\\4A-2C=6 \end{cases}$ Step 5. Solve the above equations: equation3 gives $2A-C=3$ add it to equation2 gives $2A-2B=4$ or $A-B=2$, combine with equation1 to get $A=1, B=-1$, thus $C=-1$ Step 6. The final result is: $\frac{1}{x-2}-\frac{x+1}{x^2+4}$
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