Prove that:

where x is a set and is the power set of x.

This is the last part of the question, the former parts required me to prove:

where x and y are sets.

I can't get anywhere with this! I've tried using but I can't get it to work out. My main problem is that the first three parts of the questions gave me something to work with (ie. condition 1 allows me to use ). The last part doesn't give me any properties to use so i'm having some trouble trying to use the things I already know.

Does anyone have any ideas?