\(\Leftrightarrow\left\{{}\begin{matrix}x\cdot\dfrac{5}{2}=-1\\x-y=-1\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{2}{5}\\y=x+1=-\dfrac{2}{5}+1=\dfrac{3}{5}\end{matrix}\right.\)
\(\left\{{}\begin{matrix}\dfrac{3}{2}x+y=0\\x-y=-1\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}\dfrac{5}{2}x=-1\\x-y=-1\end{matrix}\right.\) ( cộng đại số nhé pạn )
\(\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{2}{5}\\-\dfrac{2}{5}-y=-1\end{matrix}\right.\) \(\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{2}{5}\\y=\dfrac{3}{5}\end{matrix}\right.\)
