<=>\(\left\{{}\begin{matrix}4x+3y=11\\4x-y=7\end{matrix}\right.\)
<=>\(\left\{{}\begin{matrix}4y=4\\4x-y=7\end{matrix}\right.\)
<=>\(\left\{{}\begin{matrix}y=1\\4x-1=7\end{matrix}\right.\)
<=> \(\left\{{}\begin{matrix}y=1\\4x=8\end{matrix}\right.\)
<=>\(\left\{{}\begin{matrix}y=1\\x=2\end{matrix}\right.\)
vậy hệ đã cho có nghiệm (x;y) = (2;1)