1. The problem statement, all variables and given/known data By computing ∇(1/r) show that ∫∇²(1/r).dV = -4Pi if the volume 'V' is a sphere containing the origin. 3. The attempt at a solution ∫∇²(1/r).dV = ∫∇(1/r).dS But I cant differentiate (1/r) since the sphere contains the origin. Im wondering if there's any other way to tackle this.