Shortest Distance Between Two Skew Lines

Question 1

Let l1 and l2 be two skew lines with equations r=a1+ñb1 and r=a2+ub2
In vector form

Answer 1

d=|(b1×b2).(a2 ×a1)| /||b1 x b2||

Question 2

In cartesian form

Answer 2

||x2 −x1 y2 −y1 z2 −z1|
|a1 b1 c1 |
|a2 b2 c2||/
|sqrt(b1c2 −b2c1)^2 +(c1a2 −c2a1)^2 +(a1b2 −a2b1)^2|