Question

Which table represents a relation that is not a function?

Answer 1

In a function, each input or x value can have only one output or y value. For instance, when x = 10, y can't equal both 5 and 1. That would be one input producing multiple outputs. Look at answer choice D. See how the x-value of 3 has TWO corresponding y-values? Therefore, that's NOT a function.

Answer 2

A table of values is not going to be a function if two y values have the same x value.

If you run a vertical line through the x and get 2 y values, you are not dealing with a function. The one that does that is D. You have 3 and the two y values for x = 3. Those two y values are -4 and 0.