\(\Rightarrow3x^2+3y^2=10xy\\ \Rightarrow3x^2-10xy+3y^2=0\\ \Rightarrow\left(x-3y\right)\left(3x-y\right)=0\\ \Rightarrow\left[{}\begin{matrix}x=3y\\3x=y\end{matrix}\right.\)
Với \(x=3y\Leftrightarrow M=\dfrac{3y-y}{3y+y}=\dfrac{2y}{4y}=\dfrac{1}{2}\)
Với \(3x=y\Leftrightarrow M=\dfrac{x-3x}{x+3x}=\dfrac{-2x}{4x}=-\dfrac{1}{2}\)