Resolve into partial fractions:

x^4 / (x^2 +1)(x^2 -1)

sorry if it looks messy but im not sure how to make fractions, etc. on this forum

anyway, since its a improper fraction i got the proper fraction by long devision and ended up with :

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

since i cant factorize (x^2 +1) how do i continue?

do I just say A/(x^2 +1) + B/(x^2 -1) ?

If so how do i calculate values if i have B(x^2 +1) ?