How do you integrate int (6x+5) / (x+2) ^46x+5(x+2)4 using partial fractions?

1 Answer
Mar 30, 2016

int(6x+5)/(x+2)^4 dx = int (6/(x+2)^3-7/(x+2)^4)dx = -2/(x+2)^2+7/(3(x+2)^3) + C6x+5(x+2)4dx=(6(x+2)37(x+2)4)dx=2(x+2)2+73(x+2)3+C

Explanation:

(6x+5)/(x+2)^4 = A/((x+2)) + B/(x+2)^2 +C/(x+2)^3 +D/(x+2)^4 6x+5(x+2)4=A(x+2)+B(x+2)2+C(x+2)3+D(x+2)4

A(x+2)^3 + B(x+2)^2 +C(x+2) + D = 6x+5A(x+2)3+B(x+2)2+C(x+2)+D=6x+5

Ax^3 = 0x^3 rArr A=0Ax3=0x3A=0

Bx^2 = 0x^2 rArr B=0Bx2=0x2B=0

Cx = 6x rArr C=6Cx=6xC=6

2C+D=5 and C=6 rArr D=-72C+D=5andC=6D=7

Now evaluate int(6(x+2)^-3 - 7(x+2)^-4) dx(6(x+2)37(x+2)4)dx to get

-2/(x+2)^2+7/(3(x+2)^3) + C2(x+2)2+73(x+2)3+C