posted by Stephanie .
If a line segment has endpoints A(3x+5,3y) and B(x-1,-y), what are the coordinates of the midpoint of line segment AB?
The midpoint of a line segment is just halfway from A to B. So, the coordinates are just the average of the endpoints.
If C = midpoint of AB then
C = ((3x+5 + x-1)/2,(3y + -y)/2)
= ((4x+4)/2,2y/2) = (2x+2,y)