Hi guys, I've been struggling with this proof for some quite time now. I have to prove that x + y + xy = 36; has no solution in Natural numbers. I've started with proving that both x and y have to be even numbers (which is easy to prove) but now I'm going in circles. The problem is, that there are even numbers which are solution to this equation ( -2 and -38, if I recall correctly). Any ideas here?