function or not function
2. (2, -1), (2, 5), (-3, 7), (-10, 0)
3. (-2, -3), (-9, 5), (-9, 4), (-1, 10)
4. (2, 5), 1, 5), (3, 5), (-1, 5)
5. (3, 3), (3, 5), (3, 1), (3, 0)​