\(\left\{{}\begin{matrix}\left|x\right|+4\left|y\right|=18\\3\left|x\right|+\left|y\right|=10\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}3\left|x\right|+12\left|y\right|=54\\3\left|x\right|+\left|y\right|=10\end{matrix}\right.\\ \Leftrightarrow\left\{{}\begin{matrix}11\left|y\right|=44\\\left|x\right|+4\left|y\right|=18\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\left|y\right|=\dfrac{44}{11}=4\\\left|x\right|=18-4.4=2\end{matrix}\right.\\ Vậy:\left\{{}\begin{matrix}\left[{}\begin{matrix}x=2\\x=-2\end{matrix}\right.\\\left[{}\begin{matrix}y=4\\y=-4\end{matrix}\right.\end{matrix}\right.\\ Nên:\left(x;y\right)=\left\{\left(2;4\right);\left(-2;-4\right);\left(2;-4\right);\left(-2;4\right)\right\}\)
