# Recognizing functions

9 videos

2 skills

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

### Testing if a relationship is a function

VIDEO
2:23 minutes

Sal determines if points on a graph represent a function.

### Relations and functions

VIDEO
6:57 minutes

Sal determines if a relation given by a set of ordered pairs is a function.

### Checking if a set of points represents a function

VIDEO
4:07 minutes

Sal checks whether a given set of points can represent a function. For the set to represent a function, each domain element must have one corresponding range element at most.

### Checking if a table represents a function

VIDEO
1:16 minutes

Sal determines if y is a function of x from looking at a table.

### Recognize functions from tables

PRACTICE PROBLEMS

Determine whether a table of values of a relationship represents a function.

### Is this a function? (verbal description of equation)

VIDEO
1:31 minutes

Sal checks whether y can be described as a function of x if y is always three more than twice x.

### Checking if two quantities represents a function: heights

VIDEO
4:40 minutes

Sal checks whether a table of people and their heights can represent a function that assigns a height to a name.

### Checking if two quantities represents a function: price & cost

VIDEO
3:23 minutes

Sal checks whether a description of the price of an order can be represented as a function of the shipping cost.

### Checking if an equation represents a function

VIDEO
3:33 minutes

Sal determines if y is a function of x from looking at an equation.

### Does a vertical line represent a function?

VIDEO
1:40 minutes

Sal explains why a vertical line *doesn't* represent a function.

### Recognize functions from graphs

PRACTICE PROBLEMS

Determine whether a given graph represents a function.