Once again I am stuck on a question. Thanks as always.
Find all pairs of positive integers a and b such that...
a^2 + b^2 - 7 = ab
I've done this:
a^2 - ab - (7-b^2) = 0
But after that?
I've also found two solutions:a=2, b=3 and a=3 and b=2.
But i lack a solid algebraic proof.