xy+x+y+1=7
(xy+x)+(y=1)=7
x(y+1)+(y+1)=7
(y+1)(x+1)=7
7 este numar prim.Divizoriiii intregi ai lui 7 sunt
{-7,-1,1,7}
y+1=-7=> y=-8
x+1=-1 x=-2 (-2,-8)
y+1=-1 y=-2
y+1=-7 y=-8 (-8,-2)
y+1=1 y=0 Nu exista x a.i x*0=7
y+1=7 y=6
x+1=1 x=0
(0,6)
x+1=7 x=6
y+1=1 y=0
(6,0)
