Understanding Functions and Their Properties

Not a Function

Every input has only ONE output.

Not a Function

Function

No, because the x-value 11 has two y-values pair with it.

A relation where each input has exactly one output.

f(x) = 2x + 3 is a function because each x-value has one corresponding y-value.

A relation where at least one input has more than one output.

Use the vertical line test: if a vertical line crosses the graph more than once, it's not a function.

The set of all possible input values (x-values) for the function.