a, \(\left\{{}\begin{matrix}3x+5y=3\\5x+2y=1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}6x+10y=6\\25x+10y=5\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x+5y=3\\19x=-1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{-3}{19}+5y=3\\x=\dfrac{-1}{19}\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{12}{19}\\x=\dfrac{-1}{19}\end{matrix}\right.\)
Vậy hpt có nghiệm (x;y)=(-1/19;12/19)
b, \(\left\{{}\begin{matrix}6\left(x+y\right)=8+2x-3y\\5\left(x-y\right)=5+3x+2y\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}6x+6y-2x+3y=8\\5x-5y-3x-2y=5\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}4x+9y=8\\2x-7y=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}4x+9y=8\\4x-14y=10\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}23y=-2\\2x-7y=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{-2}{23}\\x=\dfrac{101}{46}\end{matrix}\right.\)
Vậy hpt có nghiệm (x;y) = ( 101/46;-2/23)
