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: 26

Answer

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

Work Step by Step

Step 1. Factor the denominator as $(x+2)(x+3)(2x-3)$ Step 2. Assume the end results as $\frac{A}{x+2}+\frac{B}{x+3}+\frac{C}{2x-3}$ Step 3. Combine the above functions as: $\frac{A(x+3)(2x-3)+B(x+2)(2x-3)+C(x+2)(x+3)}{(x+2)(x+3)(2x-3)}= =\frac{(2A+2B+C)x^2+(3A+B+5C)x+(-9A-6B+6C)}{(x+2)(x+3)(2x-3)}$ Step 4. Compare the above result with the original to set up the following system of equations: \begin{cases} 2A+2B+C=-3 \\ 3A+B+5C=-3 \\ -9A-6B+6C=27 \end{cases} Step 5. Multiple 3 to the first equation and add it to the last equation, also multiply 6 to the second equation and add it to the last equation, we get: \begin{cases} -3A+9C=18 \\ 9A+36C=9 \end{cases} or \begin{cases} -A+3C=6 \\ A+4C=1 \end{cases} Step 6. Use substitution to solve the above equations and get $A=-3, B=1, C=1$ Step 7. Conclusion: the end result is: $\frac{-3}{x+2}+\frac{1}{x+3}+\frac{1}{2x-3}$
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