Question

Integration: Out of the following methods, substitution/ parts/ partial fractions, which methods would you choose to solve each of these integrals?
1) x^2 dx / (x^2+x-2)
2) dx / (x^3+9x)
3) dx / (x^4-a^4)
4) (x^2+1) / (x^3+8)

And can you explain why please? Thank you :)