# How do you determine if the following sets of points is a function: #{(2,3), (-1, 3), (4, 7), (-1, 5)}#?

##### 1 Answer

Sep 30, 2014

Each of the domain values, x, should only output a single unique range value, y.

This example is a relation and not a function because the the domain value of -1 output 2 distinct range values.

-1 outputs a 3

and

-1 outputs a 5

If I were to draw a vertical line at the domain value of -1 that vertical line would intersect the points (-1,3) and (-1,5). Which indicates that the relation is not a function.