? = semnul inmultit (×)
(2x+1) ×(y-12) = 21 = 3×7= 7×3= 21×1 = 1×21
2x+1 = 3 ==> x = 1
y-12 = 7 ==> y = 19
2x+1 = 7 ==> x = 3
y-12 = 3 ==> y = 15
2x+1 = 21 ==> x = 10
y-12 = 1 ==> y = 13
2x+1 = 1 ===> x = 0
y-12 = 21 ==> y = 33
avem urmatoarele solutii naturale:
(x;y) = (1;19) ; (3;15); (10;13); (0;33) .