Grade 8 · Unit 3~44 min2 topics · 2 videos

Functions

Meet functions. You'll learn that a function pairs each input with exactly one output, use the vertical line test, and compare linear and nonlinear functions from tables, graphs, and equations.

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Work through these

Topics in this unit

Each topic is a short page: read the walkthrough, watch the video, try the practice, then take a quick quiz. Go in order or jump to what you need.

Introduction to Functions

A function gives exactly one output for each input.

1 video
Practice
2-question quiz
~22 min

Linear & Nonlinear Functions

Tell straight-line functions apart from curved ones.

1 video
Practice
2-question quiz
~22 min

Goals

Learning objectives

By the end of this unit, you should be able to:

Define a function as a rule with exactly one output per input.
Determine whether a relationship is a function (vertical line test).
Identify linear functions and distinguish them from nonlinear ones.
Interpret functions from tables, graphs, and equations.

Key vocabulary

Function: A rule that assigns exactly one output to each input.
Input / output: The value you put in (x) and the value you get out (y).
Vertical line test: If a vertical line hits a graph more than once, it is not a function.
Linear function: A function whose graph is a straight line; can be written y = mx + b.

More practice

External resources

Hand-picked links from Khan Academy and trusted worksheet libraries.

Khan Academy

Functions practice

Open resource

Khan Academy

Linear equations & functions

Open resource

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