Precalculus: Mathematics for Calculus, 7th Edition

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

Chapter 10 - Section 10.7 - Partial Fractions - 10.7 Exercises - Page 750: 35

Answer

$\frac{3}{x+2}-\frac{1}{(x+2)^2}-\frac{1}{(x+3)^2}$

Work Step by Step

Step 1. As the denominator has already been factorized, assume the end results as: $\frac{A}{x+2}+\frac{B}{(x+2)^2}+\frac{C}{x+3}+\frac{D}{(x+3)^2}$ Step 2. Combine the above functions as: $\frac{A(x+2)(x+3)^2+B(x+3)^2+C(x+2)^2(x+3)+D(x+2)^2}{(x+2)^2(x+3)^2}=\frac{(A+C)x^3+(8A+B+7C+D)x^2+(21A+6B+16C+4D)x+(18A+9B+12C+4D)}{(x+2)^2(x+3)^2}$ Step 3. Compare the above result with the original expression to set up the following system of equations: \begin{cases} A+C=3 \\ 8A+B+7C+D=22\\21A+6B+16C+4D=53\\18A+9B+12C+4D=41 \end{cases} Step 5. Use substitution $C=3-A$ for last three equations to get: \begin{cases} A+B+D=1\\5A+6B+4D=5\\6A+9B+4D=5 \end{cases} Step 6. Take the difference between the last two equations to get $A+3B=0$ or $A=-3B$, use this substitution for the first two equations and solve the remaining variables to get $A=3,B=-1,C=0,D=-1$ Step 7. Write the final results as: $\frac{3}{x+2}-\frac{1}{(x+2)^2}-\frac{1}{(x+3)^2}$
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