What's a Function?
If you checked out the intro to functions lesson, you may remember that a function takes an input value and assigns an output value.
Representing Functions with Mappings
One important rule to remember about a function is that it can only assign ONE output value to an input value. The set of all input values is called the domain and the set of all output values is called the range.
There are several different ways to represent a function. One way is to use a mapping diagram. A mapping diagram uses arrows to show which input and output values are paired up.
In this example, the arrows tell you what you'll get when you enter a code into the vending machine. There are two slots right next to each other that hold pretzels, so you can enter the code D3 or D4 to get a bag of pretzels. If you enter the code C2, you'll get a bag of chips.
Remember, a function can only assign one output value to an input value. Here's an example of a mapping that does NOT represent a function:
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