# Is (2,3),(-4,5),(2,-7),(7,-2) a function?

##### 1 Answer

Oct 31, 2015

No

#### Explanation:

A function is a relation (set of ordered pairs) in which each x, or domain, will yield exactly one y, or range.

Let's say you had a function y=2x+3. When you plug in any value for x, you should have exactly one y. (When x=2, y=7. Nothing else.)

But in the set of points (relation) that you gave above, there are two points that have the same domain (2,3) and (2,-7) of 2. These points would be plotted on the same vertical line on a graph, which is what we call an undefined line.

BUT you can have two points that have the same y-value, or range. Just not the same x-value. (7,9) and (8,9) would still be a function.