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# Common Core Standards: Math

# Math.CCSS.Math.Content.8.F.A.1

**1. Understand that a function is a rule that assigns to each input exactly one output. The graph of a function is the set of ordered pairs consisting of an input and the corresponding output. (Function notation is not required in Grade 8.)**

In our super-cyber information age, virtually everyone can work a computer. We have preteens learning code, preschoolers using iPads, and even grandma has branched out from solitaire to Facebook and Twitter ("@PriceIsRight just isn't the same without Bob Barker #disappointment").

In fact, many of your students are probably familiar with the computer science acronym GIGO. It stands for, "Garbage In, Garbage Out," meaning that a computer will do exactly what you tell it to do—not what you *want* it to do. If you put garbage in, you'll get garbage out.

In math, there are equations called functions that act a lot like computers. A **function** is a mathematical rule that assigns exactly one *y* value (the "output") to each *x* value (the "input"). The thing to remember about functions is that each *x* can have **one and only one** *y*. Though, interestingly enough, each *y* can have lots of *x* values, if you want.

Students should understand the concept of functions as having one output for every input. They should also be able to find the output value for a particular *x* value by plugging the number into the function wherever it has an *x*. It's also important that they know that the graph of a function represents all the ordered pairs (the different inputs-output combinations) that satisfy the function rule.

Warn your students not to try inputs and outputs of garbage. Those won't satisfy anything.