The x-coordinate of the midpoint is the average of the x-coordinates
of the ends.
The average of the ends is 1/2(-3+0) = -1.5 .
The y-coordinate of the midpoint is the average of the y-coordinates
of the ends.
The average of the ends is 1/2(-4+2) = -1
The midpoint of the segment is (-1.5, -1).
