How do you integrate (x^2+12x-5)/((x+1)^2(x-7))x2+12x5(x+1)2(x7) using partial fractions?

1 Answer
Nov 27, 2016

The answer is =-2/(x+1)-ln∣x+1∣+2ln∣x-7∣ + C=2x+1lnx+1+2lnx7+C

Explanation:

Let's do the decomposition into partial fractions

(x^2+12x-5)/((x+1)^2(x-7))=A/(x+1)^2+B/(x+1)+C/(x-7)x2+12x5(x+1)2(x7)=A(x+1)2+Bx+1+Cx7

=(A(x-7)+B(x+1)(x-7)+C(x+1)^2)/((x+1)^2(x-7))=A(x7)+B(x+1)(x7)+C(x+1)2(x+1)2(x7)

Therefore,

x^2+12x-5=A(x-7)+B(x+1)(x-7)+C(x+1)^2x2+12x5=A(x7)+B(x+1)(x7)+C(x+1)2

Let x=-1x=1, =>, -16=-8A16=8A

Coefficients of x^2x2, 1=B+C1=B+C

Let x=7x=7, =>, 128=64C128=64C

C=2C=2

B=1-C=1-2=-1B=1C=12=1

A=2A=2

(x^2+12x-5)/((x+1)^2(x-7))=2/(x+1)^2-1/(x+1)+2/(x-7)x2+12x5(x+1)2(x7)=2(x+1)21x+1+2x7

So,

int((x^2+12x-5)dx)/((x+1)^2(x-7))=int(2dx)/(x+1)^2-intdx/(x+1)+int(2dx)/(x-7)(x2+12x5)dx(x+1)2(x7)=2dx(x+1)2dxx+1+2dxx7

=-2/(x+1)-ln∣x+1∣+2ln∣x-7∣ + C=2x+1lnx+1+2lnx7+C