\(\Leftrightarrow\left\{{}\begin{matrix}3x-y=1\\5x+3y=11\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}9x-3y=3\\5x+3y=11\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}14x=14\\3x-y=1\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=1\\3.1-y=1\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x=1\\y=2\end{matrix}\right.\)
\(\left\{{}\begin{matrix}3x-\left|y\right|=1\\5x+3y=11\end{matrix}\right.\)
TH1 \(\left|y\right|>0\)
\(\left\{{}\begin{matrix}3x-y=1\\5x+3y=11\end{matrix}\right.\\ =>\left\{{}\begin{matrix}9x-3y=3\\5x+3y=11\end{matrix}\right.\\ =>\left\{{}\begin{matrix}9x+5x=3+11\\3x-y=1\end{matrix}\right.\\ =>\left\{{}\begin{matrix}x=1\\y=2\end{matrix}\right.\)
TH2 \(\left|y\right|< 0\)
\(\left\{{}\begin{matrix}3x+y=1\\5x+3y=11\end{matrix}\right.\\ =>\left\{{}\begin{matrix}9x+3y=3\\5x+3y=11\end{matrix}\right.\\ =>\left\{{}\begin{matrix}9x-5x=3-11\\3x+y=1\end{matrix}\right.\\ =>\left\{{}\begin{matrix}x=-2\\y=7\end{matrix}\right.\)
Vậy khi y>0 thì x=1 và y=2
khi y<0 thì x=-2 và y=7
