1st year linear algebra question

[michaelgtozer]

given P(-1,1,2), Q(-3,0,4), R(3,2,1), find an equation of the line through P that is parallel to the line through Q and R.

All the words after the given three points really confuse me and I just need some help on where to start to tackle this problem.

Thanks

 

[Ackbach]

Geometrically, you need to find a line going through P. But not just any line will do - it's got to be parallel to another line. Which line does it need to be parallel to? The one going through Q and R. So, Step One would be to find the line going through Q and R.

 

[mathwonk]

since 2 days have passed, maybe more detailed help is warranted. basic facts: point - point = vector parallel to the line through the two points. point + vector = another point on the line through the first point and having the given direction vector.

In general you can subtract 2 points and get a direction vector; and you can add a vector to a point to get another point on the line through the given point and parallel to the given vector.oops a year has passed!