Partial Fractions - Solving Homework Equation with Coefficients

[cragar]

Homework Statement

1/((x^2-1)^2)

Homework Equations

The Attempt at a Solution

so i get (Ax+B)/(x^2-1) + (Cx+D)/((x^2-1)^2)

then i multiply both sides by ((x^2-1)^2)
then i get 1=(Ax+B)(x^2-1)+ (Cx+D)

then i multiply it out Ax^3+Bx^2 -Ax +Cx +D =1
then i equate the coeffcients
A=0 B=0 -A+C=0 -B+D=1 D=1

but when i plug these back in i don't get what my book gets and i setting this up correctly

 

[lurflurf]

that should be
1/((x^2-1)^2)=A/(x+1)+B/(x+1)^2+C/(x-1)+D/(x-1)^2

 

[cragar]

ok i see