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: 33

Answer

$\frac{4}{x+2}-\frac{4}{(x-1)}+\frac{2}{(x-1)^2}+\frac{1}{(x-1)^3}$

Work Step by Step

Step 1. Assume the end results as: $\frac{A}{x+2}+\frac{B}{(x-1)}+\frac{C}{(x-1)^2}+\frac{D}{(x-1)^3}$ Step 2. Combine the above functions as: $\frac{A(x-1)^3+B(x+2)(x-1)^2+C(x+2)(x-1)+D(x+2)}{(x+2)(x-1)^3}=\frac{(A+B)x^3+(-3A+C)x^2+(3A-3B+C+D)x+(-A+2B-2C+2D)}{(2x+3)^2}$ Step 3. Compare the above result with the original expression to set up the following system of equations: \begin{cases} A+B=0\\ -3A+C=-10\\ 3A-3B+C+D=27\\ -A+2B-2C+2D=-14 \end{cases} Step 4. Use substitutions $B=-A, C=3A-10$ to get \begin{cases} 3A+3A+(3A-10)+D=27\\ -A-2A-2(3A-10)+2D=-14 \end{cases} or \begin{cases} 9A+D=37\\ 9A-2D=34 \end{cases} Step 5. Solve the equations to get $A=4, B=-4, C=2, D=1$ Step 6. Write the final results as: $\frac{4}{x+2}-\frac{4}{(x-1)}+\frac{2}{(x-1)^2}+\frac{1}{(x-1)^3}$
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