Assignment:
Determine whether each relation is a function. In addition, provide reasons for identifying a relation as a function.
1. {(3, 4), (5, 9), (9, 9), (2, 3)}
2. {(0, 0), (0, 1), (1, 4), (2, 4)}
3. {(2, 1), (4, 5), (8, 4), (1, 0)}
4. {(8, 3), (8, 0), (7, 7), (4, 7)}
Provide complete and step by step solution for the question and show calculations and use formulas.