Simple Linear Algrebra find a point

1. Jun 12, 2008

krisrai

1. The problem statement, all variables and given/known data
Given the two points P(-4,-5,0) and Q(5,5,-3) find the point R that is 1/4 of the way from Q to P.

2. Relevant equations

PQ = Point Q- Point P

3. The attempt at a solution
I got my direction vector as
PQ= [9,10,-3]

but i dont know how to find R

All i know is that the answer is supopsed to be:
R(2.75,2.5,-2.25)

Im wanted to add 1/4 of my direction vector PQ to my point q but this doesnt give me the right answer

2. Jun 12, 2008

tmc

Your vector is from P to Q. You want a vector from Q to P (so, QP=[-9,-10,3]).
Then, R = Q + 1/4*QP.

3. Jun 12, 2008

armis

When you calculate your direction vector $$\vec{PQ}$$ you actually get a vector which starts at point (0.0) and ends at the vector coordinates you get which in your case are (9,10,-3)