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# Identify Domain and Range Lesson Plan - 8th Grade Math

## Overview

In this lesson, students will learn how to identify domain and range from a mapping diagram, list of ordered pairs, or a graph. You can expect this lesson with additional practice to take one `45`-minute class period.

Linear Relationships And Functions
8.F.A.1

## Objective

Students will be able to identify the domain and range of a given relation.

## Materials

• Teacher slideshow
• Online Practice

## How to Teach Identifying Domain and Range

### Warm Up

To start the lesson and activate students’ prior knowledge, ask students what they already know about relations and functions. You can have students write down their thoughts or discuss it with a partner.  ### Discuss

Hopefully students recognize that relations and functions are a way of relating two variables, `x` and `y`. Bring up vocabulary such as input/output, independent/dependent, and `x`- and `y`-values. Using this as a warm up will also allow you to remind students of different ways that relations can be shown: mapping diagrams, lists of ordered pairs, and graphs.

### Introducing domain and range

Explain that domain is always the input, and range is always the output. Consider asking students whether the `x`- or `y`-value represents the domain. Similarly, which value would represent the range?

Ask students to identify the values for the input and output. You can also remind them that they do not need to repeat values, so the domain can be written as `{-9, -4, 0, 9}` instead of `{-9, -4, 0, 0, 9}`.

### Mapping diagram examples

Give students some time to try these on their own, then go over as a class. Generally, students do not struggle with mapping diagrams because the information is already organized accordingly. Let students know that they just need to list the values that represent the domain, then list the values that represent the range.

Make sure students can explain their reasoning! Consider asking students to come up with a memory trick for themselves to remember which column represents the domain and range.

### Ordered pairs examples

Allow students to try and find the domain and range for ordered pairs.

If students are struggling, it may be beneficial to ask students which number in the ordered pair represents `x` and `y` respectively.

### Graph examples

The graph is likely to cause students some confusion. It may be beneficial to remind students that the `x`-axis values for the points on the graph will represent the domain, and the `y`-axis values for the points on the graph will represent the range. Using colors for the axes may help students process the information a little easier.

### Focusing on the axes

Because domain represents `x`-values, students should focus on the `x`-axis and look to see where there are points above, below, or on it. Once students identify the `x`-values for all of the points, they should focus on the `y`-axis to find the range. Students should identify where there are points to the left, to the right, or on the `y`-axis.

### Graph Practice

The next slide gives students an opportunity to identify the domain and range of graphs with a partner or table group.

## Identifying Domain and Range Practice

After you’ve completed the examples with the whole class, it’s time for some independent practice! ByteLearn lets you access tons of practice problems for identifying domain and range. Check out the online practice and assign to your students for classwork and/or homework!  Identifying Domain and Range Practice
Problem 1 of 8

View this practice  