Question

Hai ca reuploadez intrebarea:
x=? y=?
xy+x+3(y+1)=20

Answer 1

xy+x+3(y+1)=20
x(y+1) + 3(y+1) = 20
(y+1) (x+3) = 20 = 5×4
y+1 = 5 ==> y = 4
x+3 = 4 ==> x = 1

Answer 2

daca x,y∈N, folosim divizorii naturali (1;2;4;5;10;20);
(x+3)(y+1)=20
x+3=20, x=17, 
y+1=1, y=0

x+3=10, x=7
y+1=2, y=1

x+3=5, x=2
y+1=4, y=3

x+3=4, x=1
y+1=5, y=4
variantele x+3=2 si x+3=1 nu se iau in calcul

pentru x,y∈Z se iau combinatiile in care folosim divizorii intregi:
(-1;-20), (-20;-1), (-2;-10), (-10;-2), (-5;-4); (-4;-5)
(1;20), (20;1), (2;10), (10;2), (5;4), (4;5)