Answer:
Both set A and B.
Step-by-step explanation:
Set A: (-1, 0), (-2, 1), (4, 3), (3, 4)
Set B: (1, 4), (2, 3), (3, 2), (4, 1)
Set C: (2, 1), (3, 2), (2, 3), (1, 4)
In order for (x,y) to be a function, only one x get the value of y, but many x'es can get the value y.
Looking at the set A and B, and the definition above, we can say that they are functions.
What about set C? It is not a function, as x = 2 is equal 1 or 3, which does not meet the condition from the definition.
