\(\left\{{}\begin{matrix}3x+2y=5\\2x+y=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}3x+2y=5\\4x+2y=4\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-1\\2x+y=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-1\\y=4\end{matrix}\right.\)
\(\left\{{}\begin{matrix}3x+2y=5\\2x+y=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}3x+2y=5\\-4x-2y=-4\end{matrix}\right.\)
cộng từng vế của hệ pt ta có:
\(\Leftrightarrow-x=1\Leftrightarrow x=-1\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=-1\\2x+y=2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=-1\\2\left(-1\right)+y=2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=-1\\-2+y=2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=-1\\y=4\end{matrix}\right.\)
vậy hệ pt có nghiệm \(\text{x=-1 }\)và \(y=4\)
