# Function introduction

7 videos
1 skill
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!

### What is a function?

VIDEO 7:57 minutes
Functions assign a single unique output for each of their inputs. In this video, Sal gives many examples of various kinds of functions.

### Difference between equations and functions

VIDEO 4:18 minutes
Jesse Roe and Sal talk about the difference between equations and functions

### Relations and functions

VIDEO 6:57 minutes
Relations and Functions

### Evaluating with function notation

VIDEO 11:49 minutes
Linear Function Graphs

### How to evaluate a function given its formula (example)

VIDEO 0:59 minutes
Sal evaluates f(x)=49-x^2 at x=5.

### How to evaluate a function given its graph (example)

VIDEO 0:44 minutes
Sal evaluates a function at x=-1 using the graph of that function.

### Function notation in context example

VIDEO 2:13 minutes

### Evaluating functions

PRACTICE PROBLEMS
Evaluate functions at a specific input value, given either the functions' formula or their graph.