giải hệ PT sau
\(\left\{{}\begin{matrix}x+2y=1\\-3x-y=-2\end{matrix}\right.\)
\(\left\{{}\begin{matrix}4x-5y=9\\7x+y=6\end{matrix}\right.\)
\(\left\{{}\begin{matrix}8x+2y=13\\x+y=1\end{matrix}\right.\)
\(\left\{{}\begin{matrix}5x-3y=1\\2x+y=7\end{matrix}\right.\)