\(x-y=xy-1\Leftrightarrow x-y-xy+1=0\Leftrightarrow x\left(1-y\right)+1-y=0\Leftrightarrow\left(1-y\right)\left(x+1\right)=0\Leftrightarrow\left\{{}\begin{matrix}1-y=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=1\\x=-1\end{matrix}\right.\)
Vậy x = -1; y = 1