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Date: 11/06/96 at 08:19:27
From: bonie

Hi Doc,

I would like a complete explanation of functions.

Thanks a lot, Doc!
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Date: 03/21/97 at 15:07:02
From: Doctor Matthew

Functions are one of the most important ideas in mathematics.

One of the most simple ways to think about functions is as a machine:
you put something into the machine, and it spits something back out.
For example, when I used to go to the zoo, they had these cool
machines that would make plastic gorillas while you watched. You'd put
three quarters into the machine and two minutes later a hot plastic
gorilla would fall out of the machine. This is like a function: the
input to the function was three quarters, and the output of the
function was a plastic gorilla.

So in general, a function is a set of rules for taking input and
producing output. Most of the time when you talk about functions in
math the input and output are numbers. If I've got a function called
Fred, and I input the number 5, Fred might output 10. If I input the
number 3, Fred might output 6. It just so happens that Fred is the
"take a number and double it" function. You could write this as
Fred(x) = 2x, which says that whatever the value of x is, the value of
"Fred of x" will be twice it.

You could also imagine functions that take more than one number as
their input, like f(x,y) = x+y. That means that if you give the
function numbers 8 and 5 as input, the function spits out the number
13 as output.

There's a lot more about functions out there, certainly lots more than
we can tell you right now, but there's a lot more information in our
archives.

Good luck!

-Doctors Matthew and Ken,  The Math Forum
Check out our web site!  http://mathforum.org/dr.math/
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Associated Topics:
High School Basic Algebra
High School Definitions
High School Functions
Middle School Algebra
Middle School Definitions

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