Find all possible pairs of positive integers (x,y) such that both x²+5y and y²+5x are perfect squares.

(In reply to Half an answer by e.g.)

"one of this factors is odd, and the other is even, so the product is a multiple of 4, plus 2"

16 is even; 33 is odd; if you multiply them, the product is a multiple of 4, not a multiple of 4 plus 2.

Posted by Charlie on 2006-06-03 13:09:50