In Exercises 1-20, find the midpoint M of the segment with the given endpoints.
1. G(1, 7) and H(-4,-1)
3. B(3,-4) and C(2,8)
5. R(8, -1) and S(2,9)
7. H(9, 1) and 1(-2, -3)
9. D(5, 1) and E(4, -3)​