\(\left\{{}\begin{matrix}2x+5=-\left(x+y\right)\\6x+3y=y-10\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x+5+x+y=0\\6x+3y-y=-10\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x+y=-5\\6x+2y=-10\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}6x+2y=-10\\6x+2y=-5\end{matrix}\right.\)
⇒ Hệ phương trình vô nghiệm