a. \(\left\{{}\begin{matrix}x+3y=-2\\5x-4y=11\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}5x+15y=-10\\5x-4y=11\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}19y=-21\\5x-4y=11\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=\dfrac{-21}{19}\\x=\dfrac{25}{19}\end{matrix}\right.\)
b. \(\left\{{}\begin{matrix}4x+5y=3\\x-3y=5\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}4x+5y=3\\4x-12y=20\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}17y=-17\\4x+5y=3\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=-1\\x=2\end{matrix}\right.\)
d: Ta có: \(\left\{{}\begin{matrix}x-2y=5\\2\left|x-1\right|-y=-3\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-2y=5\\4\left|x-1\right|-2y=-6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x-4\left|x-1\right|=11\\x-2y=5\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}4\left|x-1\right|=x+11\\x-2y=5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}4\left(x-1\right)=x+11\left(x\ge1\right)\\x-2y=5\end{matrix}\right.\\\left\{{}\begin{matrix}4\left(1-x\right)=x+11\left(x< 1\right)\\x-2y=5\end{matrix}\right.\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}3x=15\\x-2y=5\end{matrix}\right.\\\left\{{}\begin{matrix}-5x=7\\x-2y=5\end{matrix}\right.\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x=5\\y=0\end{matrix}\right.\\\left\{{}\begin{matrix}y=-\dfrac{7}{5}\\x=\dfrac{11}{5}\end{matrix}\right.\end{matrix}\right.\)
