Question

aflati toate perechile de nr naturale x, y pt care x-y=5, iar x este cel mult 13.

Answer 1

x=12, y=7
x=11, y=6
x=10, y=5
x=9, y=4
x=8, y=3
x=7, y=2
x=6, y=1
x=5, y=0

Answer 2

x-y=5 ⇔  y=x-5 !
daca x≤13 inseamna ca x={13; 12; 11; 10; 9 ;8; 7; 6; 5}
                          => y=x-5 = { 8;   7;   6;   5; 4; 3; 2; 1; 0) 
Raspuns:
 (x;y) = {(13;8) ; (12;7) ;(11;6) ; (10;5) ; (9;4) ; (8;3) ; (7;2) ; (6;1) ; (5;0)}