Home/Geometry/Week 1: Equations and functions/Lesson 5

Identify functions

A function is a relation where each input has exactly one output. You can identify functions from a set of points, a table, or a graph (using the vertical line test).

Lesson 5

Concept

**Function:** Each x-value is paired with only one y-value. * **{(1,2), (2,4), (3,6)}** is a function. * **{(1,2), (1,3), (2,4)}** is NOT a function, because the input 1 has two different outputs. **Vertical Line Test:** If a vertical line intersects a graph at more than one point, it is not a function.

Try it

Practice: Identify functions.