Let A = NxN, and define a relation R on A by (a,b)R(c,d) iff ab = cd.

I already proved that this is a relation.

But the question also asks to find the equivalence class E(9,2), and find an equivalence class with exactly 2 elements, one with 3 elements and one with 4 elements.

Im not sure how to do that with this question, or what that last part even means.

any help?