# Algebra I/Lines (Linear Functions)/Functions and Relations

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Back to Table of Contents Algebra I

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## Lesson

y = x2

is this a function?

versus, y2 = x

Is this a function?

The first equation is a function because x has only one y-value, whereas the second equation has many values.

In a function, each domain value or x-value should only have one y-value, otherwise it is not a function.

Definition: *In two sets, A and B, a function is a mapping from A to B.*

This mapping, should satisfy the following conditions in order for it to be a function:

1. All the elments of set A * should* be paired with any element of set B.

2. An elemnt of set A should not be paired with more than one element of set B. (i.e. the first co-ordinates of an ordered pairs should not be repeated)