\(xy=x+y+1\)
\(\Rightarrow xy-x-y=1\)
\(\Rightarrow x\left(y-1\right)-\left(y-1\right)=1+1\)
\(\Rightarrow\left(x-1\right)\left(y-1\right)=2\)
Vì x;y thuộc Z \(\Rightarrow\left(x-1\right);\left(y-1\right)\inƯ\left(2\right)=\left\{\pm1;\pm2\right\}\)
Xét bảng
x-1 | 1 | -1 | 2 | -2 |
y-1 | 2 | -2 | 1 | -1 |
x | 2 | 0 | 3 | -1 |
y | 3 | -2 | 2 | 0 |
Vậy...........................................