Hi,

I am trying to understand the following problem:

Find the parametric vector equation of the line through $\displaystyle (2, -1, 2)$ and perpendicular to the plane $\displaystyle x-2z=5$

The equation of the line is just the point + a vector in that direction. The answer shows:

$\displaystyle (2, -1, 2) + t(1, 0, 2)$

But how do you know it's perpendicular?