\(2\left(x^2-y^2\right)+xy-y^2=7\Leftrightarrow\left(2x+2y\right)\left(x-y\right)+x\left(x-y\right)=7\)
\(\Leftrightarrow\left(3x+2y\right)\left(x-y\right)=7\)
\(\left\{{}\begin{matrix}3x+2y=7\\x-y=1\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x=\frac{9}{5}\\y=\frac{4}{5}\end{matrix}\right.\) không nguyên (loại)
\(\left\{{}\begin{matrix}3x+2y=1\\x-y=7\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x=3\\y=-4\end{matrix}\right.\)
\(\left\{{}\begin{matrix}3x+2y=-1\\x-y=-7\end{matrix}\right.\) \(\Rightarrow\left\{{}\begin{matrix}x=-3\\y=4\end{matrix}\right.\)
\(\left\{{}\begin{matrix}3x+2y=-7\\x-y=-1\end{matrix}\right.\) \(\Rightarrow x=-\frac{9}{5}\notin Z\) loại
