17 = 17 * 1
17 = 1 * 17
17 = - 17 * ( - 1)
17 = - 1 * (- 17)
1) x = 16 ; y = 3
2) x = 0 ; y = 19
3) x = - 18 ; y = 1
4) x = - 2 ; y = - 15
