A relation is considered a function if each input (the first element of each ordered pair) corresponds to exactly one output (the second element of each ordered pair).
Let's analyze the given ordered pairs:
- (19, 13)
- (–4, –12)
- (19, 12)
In this set, the input 19 appears twice:
- In the first pair, 19 corresponds to 13.
- In the third pair, 19 corresponds to 12.
Since 19 is associated with two different outputs (13 and 12), this relation does not meet the criteria for a function. Therefore, this relation is not a function.