Question

How do you know a relation is a function?

Answer 1

1.) A function can't have any repeated x-coordinates

For example:

{(3, 4), (3, 6), (5, 4)}

This is not a function because 3 is repeated.

{(2, 1) (4, 1), (5, 1)}

This is a function because the y-coordinates can be the same, but not the x-coordinates.

2.) When a function is graphed, it will only have one intersection point with a vertical line.

For examples, see the image attached.