Question

Giải hệ phương {2x+y=-1

                             {X-2y=7

Answer 1

\(\left\{{}\begin{matrix}2x+y=-1\\x-2y=7\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}4x+2y=-2\\x-2y=7\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}5x=5\\x-2y=7\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=1\\1-2y=7\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=1\\2y=-6\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=1\\y=-3\end{matrix}\right.\)

Vậy `(x,y)=(1,-3)`