Answer
The vector is parallel to the plane.
Work Step by Step
Apply orthogonality test.
This implies $n \cdot v=\lt 2,1,0 \gt \cdot \lt 2,-4,1 \gt$
or, $n \cdot v=2(2)+1(-4)+0(1)=0$
This means that the vector $v$ is orthogonal to the normal plane's normal vector $n$.
Therefore, the vector is parallel to the plane.
