Consider the lines:

L1:[xyz]T=[34−2]T+t[0−12]T

L2:[xyz]T=[5a−2]T+s[1−1−1]T

Find the value of a such that L1 and L2 lie in a plane.

Hint: What must the minimal distance between the two lines be if we are to be sure they lie in the same plane?

i don't really have a clue how to do this. I found both my direction vectors and crossed them. Yeah im just really stuck.