How to find the potential due to a nutreal conductor with a cavity inside it and point charge in the cavity?

On surface of hole , - Q1 charge is circulated consistently. 

Presently, outside this hole , the consolidated impact of the charge and the prompted charge is zero.Think of it along these lines, the charge gets disseminated on the internal surface with the end goal that it offsets the impact of charge Q1 outside the cavity. 

Along these lines, charge on thhe external surface will be +Q1 circulated uniformly.Uniform distribution(each essential charge equidistant from each other on the surface) of charge relates to least vitality of the surface and therefore is the favored arrangement.