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## Homework Statement

One of those annoying questions that should be simple, but that I've forgotten how to do:

Two lines are given by the equations

**r1**=

**a**+l

**p**and

**r2**=

**b**+m

**q**. Find the condition for the lines to cross, and find there position of intersection.

## Homework Equations

## The Attempt at a Solution

I've done the first bit: (

**a**-

**b**).(

**p***

**q**)=0 where * means the cross product. But I can't find a way of doing the second bit (find the point of intersection), I'd know how to do it if the actual vectors were given, but how do you write in in a nice vector form?

Thanks