1. The problem statement, all variables and given/known data 2. Relevant equations (x,y,z)=(x0,y0,z0) + t(m1,m2,m3) 3. The attempt at a solution So at first I thought that since vector P1P2 is at right angles to both lines, both lines must be parallel. Quickly dismissed this idea since their direction vectors are not multiples of one another. Then I thought P1P2 could be the cross product of both direction vectors... crossed both vectors and got P1P2=(-1,3,1). Not sure if that's the right approach, and not sure what to do from here. Any help would be great!