Question

Determinati perechile (x,y) de numere intregi nenule pt. care xy+x-3y+3=0

Answer 1

x(y+1) = 3y -3
x = 3(y - 1)/(y+1) 
daca (y+1) | 3    (y+1) ∈ D3    y+1 ∈ {-3, -1, 1, 3}      y ∈ {-4, - 2, 0, 2}
x ∈ {3·(-5)/(-3), 3·(-3)/(-1), 3·(-1)/1 , 3·1/3 }
x ∈ {5, 9, -3, 1}    (5,-4), (9, -2), (-3, 0), (1, 2)
daca (y+1) | (y-1) ⇒    (y+1) | (y+1-y+1)    (y+1) | 2   (y+1) ∈ D2
(y+1) ∈ {-2, -1, 1, 2}    y ∈ {-3, -2, 0, 1}    x∈{6, 9, 3, 0}
(6,-3), (9, -2), (3, 0) , (0, 1)