this may clear things up, found it very useful myself
Index of /documentsfp3/vectors%20cartesian%20eqn%20of%20a%20line.doc
A line L1 passes through point A, with position vector , and the point B, with position vector .
a) Write down equation for line L1
i got the equation of line L1 as: :
A second line L2 has equation:
b) Show that L1 and L2 are perpendicular to each other.
c) Show that the two lines meet, and find the position vector of th epoint of inersection.
I need help with parts (b) and (c) assuming my part (a) is correct.