Question

Which set of ordered pairs does not represent a function?

A (0,3), (1,3), (2,4), (3,5)
B (1,3), (2,5), (3,-1), (4,-3)
C (2,3), (2,5), (3,6), (4,7)
D (3,3), (4,5), (5,6), (6,7)

Answer 1

In a function, each x-value must be paired with exactly one y-value.
If you can find an x-value that is paired with more than one y-value, then it’s not a function.

The quick way to find the answer is to look through all the sets and see if there’s any set that uses the same x-value more than once.
For A, the x-values are 0, 1, 2, 3.
For B, the x-values are 1, 2, 3, 4.
For C, the x-values are 2, 2, 3, 4.
For D, the x-values are 3, 4, 5, 6.

Only C has a repeated x-value.