Ta có:
\(x^2-2y^2-xy=0\)
<=>\(\left(x^2-y^2\right)-\left(y^2-xy\right)=0\)
<=>\(\left(x-y\right)\left(x-y\right)-y\left(x+y\right)=0\)
<=> \(\left(x-y\right)\left(x-2y\right)=0\)
<=> x - 2y = 0 ( do x+y khác 0 )
<=> x =2y
Thay vào đề bài ta có
Q=\(\frac{2y-y}{2y+y}=\frac{y}{3y}=\frac{1}{3}\)
Từ \(x^2-2y^2=xy\Rightarrow x^2-2y^2-xy=0\)
\(\Rightarrow\left(x^2-y^2\right)-\left(y^2+xy\right)=0\)
\(\Rightarrow\left(x-y\right).\left(x-y\right)-y.\left(x-y\right)=0\)
\(\Rightarrow\left(x-y\right).\left(x-2y\right)=0\)
\(\Rightarrow x=2y\)
Thay vào đã dc:\(Q=\frac{1}{3}\)