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### Recognizing a Function From a Graph

```Date: 09/03/2003 at 02:23:55
From: flora
Subject: Explain how to tell if a graph represents a function

I think I'm a bit confused about what a function is. How is it
different from an equation?
```

```
Date: 09/03/2003 at 06:13:13
From: Doctor Anthony
Subject: Re: Explain how to tell if a graph represents a function

A function requires that you get a single unique value of y for a
given value of x.  So if you draw a line, x=k (that is, a line
parallel to the y axis), and it cuts the graph in one point only for
all k, then you have a function.  If the line cuts the graph in more
than point for some values of k then we have a RELATION and not a
function.

Example of a function:   y = 3x^2 + 2x - 1

Example of a relation:   x^2 + y^2 = 4

- Doctor Anthony, The Math Forum
http://mathforum.org/dr.math/
```

```
Date: 09/04/2003 at 00:54:54
From: flora
Subject: Thank you

Thanks!  That was very clear!
```
Associated Topics:
High School Definitions
High School Functions

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