State the slope of a line parallel to a line passing through each pair of
points. Then state the slope of a line perpendicular to the line passing
through each pair of points.
15. (-1,-1), (3, 2)
18. (-7, 5), (1, 1)
22-13
16. (4, 2), (3, -1)
19. (-2, -3), (1,8)
17. (1, 5), (3, 2)
20. (-2,-2), (1, 6)