\(5x^2+y^2-4xy+2x< 0\)
\(\Leftrightarrow\left(4x^2-4xy+y^2\right)+\left(x^2+2x+1\right)< 1\)
\(\Leftrightarrow\left(2x-y\right)^2+\left(x+1\right)^2< 1\)
Vì x,yEZ\(\Rightarrow\left(2x-y\right)^2+\left(x+1\right)^2=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}2x-y=0\\x+1=0\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}x=-1\\y=-2\end{matrix}\right.\)