\(\left\{{}\begin{matrix}y=2x\\x+6=2y\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x-y=0\\x-2y=-6\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2x-y=0\\2x-4y=-12\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}3y=12\\y=2x\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}y=4\\x=2\end{matrix}\right.\)
Ta có: FH là đường trung bình hthang DECB
\(\Rightarrow y=\dfrac{x+6}{2}\Rightarrow2y=x+6\Rightarrow x=2y-6\)
Ta có: DE là đường trung bình tam giác AFH
\(\Rightarrow x=\dfrac{1}{2}y\Rightarrow2y-6=\dfrac{1}{2}y\Rightarrow\dfrac{3}{2}y=6\Rightarrow y=4\)
\(\Rightarrow x=\dfrac{1}{2}y=2\)
