Calculus of an integral

[gimanske]

Does anyone know how to solve the following integral (for the values of k>0 integer such that it exists)? Thanks!

integral from 0 to infinity of t^k/[ (t+a)^(r+1) ]dt, where a>0 and r>2

[arnaud32]

, where a>0 and r>2
use some Ipp technique