Meh, too late, no replies. Well, I still don't mind an answer to the question I guess...Two planes A and B have vector equations $\displaystyle r.(2i+j-2k)=3$ and $\displaystyle r.(2i+j-2k)=9$. Explain why A and B are parallel and hence find the distance between them.

Parallel since the perpendicular direction is equal (2i+j-2k) but I have no idea how to calculate the distance