\(xy-x+y-1=-1\Leftrightarrow\left(x+1\right)\left(y-1\right)=-1\)
\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x+1=1\\y-1=-1\end{matrix}\right.\\\left\{{}\begin{matrix}x+1=-1\\y-1=1\end{matrix}\right.\end{matrix}\right.\) ......
\(x.y=x-y\\ \Leftrightarrow xy-x+y=0\\ \Leftrightarrow x\left(y-1\right)+1\left(y-1\right)=0\\ \Leftrightarrow\left(y-1\right)\left(x+1\right)=-1\\ \cdot\left\{{}\begin{matrix}y-1=-1\\x+1=1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=0\\x=0\end{matrix}\right.\\ \cdot\left\{{}\begin{matrix}y-1=1\\x+1=-1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=2\\x=-2\end{matrix}\right.\)
