College Algebra 7th Edition

Published by Brooks Cole
ISBN 10: 1305115546
ISBN 13: 978-1-30511-554-5

Chapter 5, Systems of Equations and Inequalities - Section 5.3 - Partial Fractions - 5.3 Exercises - Page 462: 24

Answer

$\frac{7x-3}{x(x+3)(x-1)}=\frac{1}{x}+\frac{-2}{x+3}+\frac{1}{x-1}$

Work Step by Step

$\frac{7x-3}{(x^3+2x^2-3x)}$, factorising $x^3+2x^2-3x=x(x+3)(x-1)$: $\frac{7x-3}{x(x+3)(x-1)}=\frac{A}{x}+\frac{B}{x+3}+\frac{C}{x-1}$, $7x-3=A(x-1)(x+3)+Bx(x-1)+Cx(x+3)=(Ax^2+2Ax-3A)+(Bx^2-Bx)+(Cx^2+3Cx)$, $7x-3=A+B+C)x^2+(2A-B+3C)x-3A=7x-3$, $(A+B+C)x^2=0, A+B+C=0$, $(2A-B+3C)x=7x, 2A-B+3C=7$ and $-3A=-3, A=1$: substituting $A=1$ back into the equation, the first equation becomes $B+C=-1$ and the second equation becomes $-B+3C=5$: $\begin{cases} & B & +C & = -1&\\ & -B & +3C & = 5&\\ & -- & -- & -- \\ & 0 & +4C & = 4 \end{cases}$ $C=1$, substituting back into the equation, $B+1=-1, B=-2$: thus, $\frac{7x-3}{x(x+3)(x-1)}=\frac{1}{x}+\frac{-2}{x+3}+\frac{1}{x-1}$
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