How do you integrate 2(x41)dx using partial fractions?

1 Answer

2x41dx=tan1x12ln(x+1)+12ln(x1)+C0

Explanation:

2x41dx

for the partial fraction

2x41=2(x2+1)(x21)=Ax+Bx2+1+Cx+1+Dx1

2=(Ax+B)(x21)+C(x2+1)(x1)+D(x2+1)(x+1)

We now have the equation

2=Ax3+Bx2AxB+C(x3+xx21)+D(x3+x+x2+1)

and then

A+C+D=0 first equation
BC+D=0 second equation
A+C+D=0 third equation
BC+D=2 fourth equation

simultaneous solution results to

A=0
B=1
C=12
D=12

2x41dx=Ax+Bx2+1dx+Cx+1dx+Dx1dx

2x41dx=1x2+1dx+12x+1dx+12x1dx

2x41dx=tan1x12ln(x+1)+12ln(x1)+C0

God bless....I hope the explanation is useful.