\(xy-x-y=2\)
\(\Rightarrow xy-x-y+1=3\)
\(\Rightarrow x\left(y-1\right)-1\left(y-1\right)=3\)
\(\Rightarrow\left(x-1\right)\left(y-1\right)=3\)
\(\Rightarrow x-1;y-1\inƯ\left(3\right)\)
\(Ư\left(3\right)=\left\{\pm1;\pm3\right\}\)
\(\Rightarrow\left\{{}\begin{matrix}x-1=1\Rightarrow x=2\\y-1=3\Rightarrow y=4\\x-1=-1\Rightarrow x=0\\y-1=-3\Rightarrow y=-2\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x-1=3\Rightarrow x=4\\y-1=1\Rightarrow y=2\\x-1=-3\Rightarrow x=-2\\y-1=-1\Rightarrow y=0\end{matrix}\right.\)
