# Linear equations and functions

Contents
Linear equations like y = 2x + 7 are called "linear" because they make a straight line when we graph them. These tutorials introduce you to linear relationships, their graphs, and functions.

## Graphing proportional relationships

When you walk at a constant rate, the relationship between the distance you've walked and the time you've spent walking is proportional. In this tutorial, we learn about proportional relationships (constant rates) and their graphs..

## Solutions to linear equations

Learn how to figure out if an ordered pair is a solution to a linear equation.

## Intercepts

Learn about intercepts of a line. Identify intercepts using a table, graph, and equation.

## Slope

Learn about slope of a line and the slope formula. Identify slope from a graph, two points, and an equation.

## Slope-intercept form

Learn about the slope-intercept form of two-variable linear equations, and how to interpret it to find the slope and y-intercept of their line. Find the slope-intercept equation of a line from its graph, a table, or two points.

## Functions & function notation

Learn how to evaluate functions from a formula or graph. Compare linear functions.

## Linear models

Learn to use linear models to show relationships between two variables and represent them using a table, equation, or a graph.

## Recognizing functions

Relationships can be any association between sets of numbers while functions have only one output for a given input. This tutorial works through a bunch of examples of testing whether something is a valid function. As always, we really encourage you to pause the videos and try the problems before Sal does! Common Core Standard: 8.F.A.1

## Linear and nonlinear functions

Not every relationship in the universe can be represented by a line (in fact, most can't be). We call these "nonlinear". In this tutorial, you'll learn to tell the difference between a linear and nonlinear function! Have fun! Common Core Standare: 8.F.A.3