Grade+11+Block+3+Objective+4

Objective 4: Determining if a Relation is a Function

In this objective, we are learning how to determine if a relation is a function. To do this you just look at your graph and put it through the **__vertical line test__.** The vertical line test is a test that helps you determine if a relation in a function. If you can put a vertical line anywhere on the x-axis, and it only intersects the relation at one point, then it is a function.

In picture #1, each vertical line only intersects the parabola once, no matter where you put it along the x-axis. Therefore graph #1 is a function. In picture #2, each vertical line intersects the parabola twice. Therefore graph #2 is **not** a function.

This graph is another example of a relation that passes through the vertical line test, making it a function.

These are a few examples of relations that are functions because they pass the **__vertical line test.__**