How do you integrate 7x2(x3)2(x+1) using partial fractions?

1 Answer
Nov 3, 2017

Write the partial fractions equation:

7x2(x3)2(x+1)=Ax+1+Bx3+C(x3)2

Multiply both sides by (x3)2(x+1):

7x2=A(x3)2+B(x3)(x+1)+C(x+1)

Let x=1

7(1)2=A(13)2+B(13)(1+1)+C(1+1)

9=16A

A=916

7x2=916(x3)2+B(x3)(x+1)+C(x+1)

Let x=3

7(3)2=916(33)2+B(33)(3+1)+C(3+1)

#C = 19/4

7x2=916(x3)2+B(x3)(x+1)+194(x+1)

Let x=0

7(0)2=916(03)2+B(03)(0+1)+194(0+1)

2=81163B+194(0+1)

B=916

The partial fractions are:

7x2(x3)2(x+1)=9161x+1+9161x3+1941(x3)2

Integrate:

7x2(x3)2(x+1)dx=9161x+1dx+9161x3dx+1941(x3)2dx

The integrals are trivial:

7x2(x3)2(x+1)dx=916lnt|x+1|+916ln|x3|1941x3+C