which sets of ordered pairs are functions and which are not functions? 1. { (1,5),(2,5),(3,5),(4,5) } 2. { (1,5),(1,6),(1,7),(1,8) } 3. { (1,6),(2,5),(2,3),(4,8) } 4. { (1,5),(3,7),(4,8),(4,9) }