d) Ta có: \(\left\{{}\begin{matrix}2x-y=-7\\3x+y=27\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}5x=20\\2x-y=-7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=4\\y=2x+7=15\end{matrix}\right.\)
e) Ta có: \(\left\{{}\begin{matrix}x+2y=4\\-3x+y=7\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x+6y=12\\-3x+y=7\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}7y=19\\x+2y=4\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{19}{7}\\x=4-2y=4-\dfrac{38}{7}=\dfrac{-10}{7}\end{matrix}\right.\)
a) Ta có: \(\left\{{}\begin{matrix}x-y=-5\\2x+y=11\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x=6\\x-y=-5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=2-\left(-5\right)=7\end{matrix}\right.\)
b) Ta có: \(\left\{{}\begin{matrix}x-2y=3\\x+y=6\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}-3y=-3\\x+y=6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=1\\x=5\end{matrix}\right.\)
c) Ta có: \(\left\{{}\begin{matrix}4x-3y=1\\-x+3y=2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x=3\\3y-x=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\3y=2+x=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=1\end{matrix}\right.\)
f) Ta có: \(\left\{{}\begin{matrix}3x+2y=1\\3x+y=2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=-1\\3x+y=2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=-1\\3x=2-y=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=-1\end{matrix}\right.\)
