I am going through my Quantum textbook, just reviewing the material, i.e. this isn't a homework question. We are solving the radial equation for the Hydrogen Atom, first looking at the asymptotic behavior. My issue is I am completely blanking on how to solve the differential equation: d^2u/dp^2 = [l(l+1)/p^2]u. The general solution is: u(p) = Cp^(l+1) + Dp^-l. Can someone walk me through the steps of getting to this general solution? Thank you!