To determine whether a given set of ordered pairs represents a function, we need to check if each input (the first element of each pair) corresponds to exactly one output (the second element of each pair).
In the first set you provided:
{ (0, -4), (2, 7), (0, 4), (1, 9), (3, 7) }
The first element "0" appears twice with two different outputs: -4 and 4. This means that for the input 0, there are two different outputs, which violates the definition of a function.
Therefore, the set does not represent a function.