Hello,How can i solve this problem? I have tried to solve with mathematica but it does not answer correctly Could you kindly help me?
Just use the modified operator D[expr, r, r] + 1/r D[expr, r] - 4/r^2 expr.
D[expr, r, r] + 1/r D[expr, r] - 4/r^2 expr
Thank you very much it is correct. Also could you help me on this?
I think that it is an operator square, not a numeric square:
op[expr_, r_] := D[expr, r, r] + 1/r D[expr, r]; DSolve[op[op[f[r], r], r] == 0, f, r]