#### What is the Vertical Line Test for Functions?

**Answer:** A method to distinguish functions from relations.

The vertical Line test.

- is a way to determine if a relation is a function.
- states that if a vertical line intersects the graph of the relation more than once, then the relation is a NOT a function.

If you think about it, the **vertical line test** is simply a restatement of the definition of a function.

**Definition of a function:** Every x value has a unique y value.

*Think about it* If any particular x value has 2 different y values, then a vertical line will intersect the at two different places.

Let's examine the two relations below this These two relations differ by only 1 number!