1 Which set of ordered pairs does not represent a function?
1 {(1, 10), (3, 18), (5, 26), (7, 34), (9, 42)
2 {(2, 10), (3, 20), (4, 15), (5,5), (6,25)
3 {(0,8), (5,4), (10,0), (15, 4), (20,8)
4 {(9, 1), (6,2), (3, 3), (6,4), (9,5)}