\(\left\{{}\begin{matrix}x+y=5\\2x-3y=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x+2y=10\\2x-3y=0\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}5y=10\\x+y=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=2\\x+y=3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}y=2\\x=3\end{matrix}\right.\)
Vậy hpt có 1 cặp nghiệm (x;y)=(3;2)
\(\left\{{}\begin{matrix}2x-y=3\\3x+5y=11\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}10x-5y=15\\3x+5y=11\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}13x=26\\2x-y=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=2x-3\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}x=2\\y=2.2-3\end{matrix}\right. \Leftrightarrow\left\{{}\begin{matrix}x=2\\y=1\end{matrix}\right.\)
Vậy hpt có 1 cặp nghiệm (x;y)=(2;1)
