Question

A,B,C are collinear points and AB=BC. If A is the point (4,5) and B is the point (1,-1) find the coordinates of C.

Answer 1

B is the midpoint of AC. So, its coordinates are the average of the endpoints. So, if C=(x,y) we have

(x+4)/2 = 1
(y+5)/2 = -1

Now just solve for x and y.