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Relations and Functions

When Is a Relation a Function?


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Jennifer Ledwith

A relation is a set of data. A function is a set of data that has one distinct output for each input. A relation is a function when an input appears only once in the data set. Here are some examples of relations:

  1. Collection of points:
    {(-1,2), (-2,4), (-3,6), (-1,-2)}
  2. Table: Look at the table, Number of text messages sent.
  3. Graph: Click on More Images and view the graph, Advertising Campaign Results.

Please realize that all functions are not lines. Rolling hills, v-shaped pictures, u-shaped diagrams -these are other functions that you'll explore as an Algebra student.

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