a: Ta có: \(\left\{{}\begin{matrix}4x+y=2\\8x+3y=5\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}8x+2y=4\\8x+3y=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-x=-1\\4x+y=2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=2-4x=2-4\cdot1=-2\end{matrix}\right.\)
b: Ta có: \(\left\{{}\begin{matrix}3x-2y=11\\4x-5y=3\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}12x-8y=44\\12x-15y=9\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}7y=35\\3x-2y=11\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=5\\3x=11+2y=21\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=7\\y=5\end{matrix}\right.\)
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