Question

Which of the sets of ordered pairs represents a function?

A = {(2, −2), (5, −5), (−2, 2), (−5, 5)}
B = {(4, 2), (4, −2), (9, 3), (9, −3)}

Only A
Only B
Both A and B
Neither A nor B

Answer 1

check each list to make sure each unique x-value is only assigned one y-value (two x's can share the same y' value but you can't assign the same x-value to multiple y-values)

Answer 2

for example, this is a function:

{(1,2), (2,2)} since it's two different x's assigned to the same y-value

but this is not a function:

{(1,2),(1,3)}