8th Grade: Introducing Relations and Functions

Did you miss Wednesday or Thursday this week? If you did, you missed a big day in our new unit. Please come see me in seminar or in the morning to get caught up.

On Wednesday and Thursday, we learned about relations and functions.

I started by asking everyone what comes to their mind when thinking of  the word,  "Relation."

The main idea that came to everyone's mind is relationships. When you think of the word relation, relationships should come to your mind.

A relation is a relationship between two variables. We will be primarily looking at the variables, x and y.

Then we discussed, the word "function." We decided the word function means something that works.

A function is a relation where each input has exactly one output. 

X-values are also known as domains, inputs, and independent variables.

Y-values are also known as ranges, outputs, and dependent variables.

Below are examples of relations, functions, and non-functions.

Graphs:

This graph is a relation and function.

This graph is a relation but not a function. The x-value, 0 has two y-values.

Tables:

This table is a relation and a function. Each x-value has only one y-value.

The first table is an example of a relation that is not a function. The x-value 4 has two y-values. The second table is a function. Each x-value has only one y-value, even though all y-values are the same. Remember we focus on the x-values.

Ordered Pairs:

All of the ordered pairs below are relations that function. 

Mapping Ordered Pairs: 

The mapping below shows a relation that is not a function.

Big Idea: Every function is a relation but not every relation is a function.

Have a Happy Snow Day,

Mrs. Gilliam

Class Dojo Point for Letting Me know the Correct Answer:

Is the following graph a function?