This question has stumped me, it is the only question like this in my textbook and i can't figure out how to solve this, i'm not the best at maths so any help people could give me would be great!

The vector $\displaystyle A = 3i + j - k$ is normal to the plane $\displaystyle M1 $and the vector $\displaystyle B = 2i - j + k$ is normal to a second plane $\displaystyle M2$

Do the two planes necessarily intersect if they are both extended indefinetly? If the two planes do intersect, find a vector which is parallel to their line of intersection.

Thanks guys!