\(\left\{{}\begin{matrix}4x^2-4xy+y^2=9\\x+3y=5\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\left(2x-y\right)^2=9\\x+3y=5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}2x-y=3\\x+3y=5\end{matrix}\right.\\\left\{{}\begin{matrix}2x-y=-3\\x+3y=5\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=2\\y=1\end{matrix}\right.\\\left\{{}\begin{matrix}x=-\frac{4}{7}\\y=\frac{13}{7}\end{matrix}\right.\end{matrix}\right.\)
