Which of the following sets represents a function?

{(3, 5), (-1, 7), (3, 9)}
{(1, 2), (3, 2), (5, 7)}
{(1, 2), (1, 4), (1, 6)}

Choice A is not a function because x = 3 repeats itself. We have x = 3 leading to more than one y value.

The same applies for choice C. The x value x = 1 repeats itself.

The only case where this doesn't happen is with choice B. The unique x values indicate we have a function. For any given x, there is EXACTLY ONE output.



Choice B