Help with Electric Potential 2 Homework

[asi123]

Homework Statement

Hey guys.
Look at this question, I already did the first part.
I have no idea how to do the second one, even with the clue...

Can Someone please help me with that?
10x.

Homework Equations

The Attempt at a Solution

 

[Hootenanny]

Well, the HINT suggests using integration by parts, have you tried that?

You should note that integration by parts for vector equations is not the same as for scalar equations. If you're not familiar with using integration by parts on vector equations, it is also possible to use Green's formula.

 

[olgranpappy]

Also, you will probably find one of Maxwell's equations fairly useful... The one that relates charge density to electric field.