Find, with proof, all positive integer values n such that (http://latex.sidoh.org/?render=-5%5E4%20%2B%205%5E5%20%2B%205%5En%20) is a perfect square.
EDIT: Added in the "with proof" clause because that's really in the spirit of the question.
-(5^4) or (-5)^4?
-(5^4)
n = 5 yielding 2500+5^n = 5625, which is 75^2. There are others, I'm sure, but eh?
Yep, n = 5 is one of the solutions. What are the others? Are there any others? And prove it :P