# What is a Linear Function?

A linear function is an algebraic equation in which each term is either a constant or the product of a constant and (the first power of) a single variable. For example, a common equation,

# Graphs of Linear Functions

The origin of the name "linear" comes from the fact that the set of solutions of such an equation forms a straight line in the plane. In the linear function graphs below, the constant,

## Graphs of linear functions

The blue line,

# Vertical and Horizontal Lines

Vertical lines have an undefined slope, and cannot be represented in the form

Horizontal lines have a slope of zero and is represented by the form,