Math Help - Simplifying double integral with integration by parts?

1. Simplifying double integral with integration by parts?

Can someone help me? I want to know if I can rewrite this double integral into a single integral, but I am not sure if it is possible.
Please have a look at the attached file, to see what I have tried so far.. It seems to go wrong with the last term: dV.
Any help is most welcome.
Thanks.