a) (x+1) × (y+2) = 15
(x+1) × (y+2) = 3 × 5
x+1 = 3 ==> x = 2
y+2 = 5 ==> y = 3
Verificare:
(2+1) × (3+2) = 3× 5 = 15
b) (2x+1) × (y-12) = 21
(2x+1) × (y-12) = 3 × 7
2x+1 = 3 ==> 2x = 2 ==> x = 1
y - 12 = 7 ==> y = 7+12 ==> y = 19
verificare:
(2×1+1) × (19-12) = 3 × 7 = 21
