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**Cyganek** Relation R on ℕ x ℕ

((a,b),(c,d)) R <=> a+b = c+d

Ok I had to prove that R is an equivalence relation (Reflexivity, symmetry, transtitivity). I already did that. Second part is to sketch all equivalence classes of R.

I dont understand or the way to sketch it. Do I have to draw a matrix? Or a coordinate system?

A coordinate system would simply cover the whole positive area of it. But I need to sketch the CLASSES of R so I dont think I understand it the way I should. What am I overlooking?