để x,y là số nguyên khi x-2 và y-1 \(\inƯ\left(-11\right)=\left\{-1;1;-11;11\right\}\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x-2=-1\\y-1=11\end{matrix}\right.\\\left\{{}\begin{matrix}x-2=11\\y-1=-1\end{matrix}\right.\\\left\{{}\begin{matrix}x-2=1\\y-1=-11\end{matrix}\right.\\\left\{{}\begin{matrix}x-2=-11\\y-1=1\end{matrix}\right.\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=1\\y=12\end{matrix}\right.\\\left\{{}\begin{matrix}x=13\\y=0\end{matrix}\right.\\\left\{{}\begin{matrix}x=3\\y=-10\end{matrix}\right.\\\left\{{}\begin{matrix}x=-9\\y=2\end{matrix}\right.\end{matrix}\right.\)
