Ok heres the question i am stuck on. I have tried many things and can't get it.
The points P(-2,1),Q(-6,4),and R(4,3) are three vertices of parrallelogram PQRS
a) Find the coordinates of S
You don't need to use the dot product here, in fact, all we need to do is construct the diagram.
This is what our diagram should look like: Parallelogram - Wikipedia, the free encyclopedia
So graph the points you have and label the remaining point in the vacent corner S and draw lines to it.
The height of the known side (point Q to point P) is $\displaystyle 4-1 = 3 $ and the right side of the diagram has point R at height 3. We know that, by the shape of the parallelogram S needs to be bellow R, so its height or y co-ordinate is $\displaystyle 3-3=0 $
The same procedure but for the x-cordinate between R and Q yields $\displaystyle -6-4 = -10 $. Thus, the x co-cordinate for S is $\displaystyle -2 - - 10 = 8 $
S is at (8, 0)