Do P(-1;3) thuộc d;d'
=> \(\left\{{}\begin{matrix}-m-3\left(n+1\right)-1=0\\-n+6m+2=0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}-m-3n=4\\6m-n=-2\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}m=-\dfrac{10}{19}\\n=-\dfrac{22}{19}\end{matrix}\right.\)