\(x,y\in Z\Rightarrow\left\{{}\begin{matrix}x-1\in Z\\y+2\in Z\end{matrix}\right.mà:\left(x-1\right)\left(y+2\right)=7nen:x-1\inƯ\left(7\right)\Rightarrow\left(x-1\right)\in\left\{-1;1;-7;7\right\}\) \(+,x-1=-1\Rightarrow\left\{{}\begin{matrix}x=0\\y+2=-7\end{matrix}\right.\Leftrightarrow x=0;y=-9\left(thoaman\right)\)
\(+,x-1=-7\Rightarrow\left\{{}\begin{matrix}x=-6\\y+2=-1\end{matrix}\right.\Leftrightarrow x=-6;y=-3\left(thoaman\right)\)
\(+,x-1=1\Rightarrow\left\{{}\begin{matrix}x=2\\y+2=7\end{matrix}\right.\Leftrightarrow x=2;y=5\left(thoaman\right)\)
\(+,x-1=7\Rightarrow\left\{{}\begin{matrix}x=8\\y+2=1\end{matrix}\right.\Leftrightarrow x=8;y=-1\left(thoaman\right)\)
\(Vậy:\left(x,y\right)\in\left\{\left(0;-9\right);\left(-6;-3\right);\left(2;5\right);\left(8;-1\right)\right\}\)
