Centre for Distance Learning and Innovation

A function is a relation in which each value of the independent variable (x) or domain corresponds to exactly one value of the dependent variable (y) or range.
On a graph, a function has one and only one value of y for each value of x.
The vertical line test (a method to determine if a graph models a function): "If no two points on a graph can be joined by a vertical line, the graph represents a function."
You have already studied and worked with
- constant functions
- linear functions
- quadratic functions
- absolute-value functions
- sinusoidal functions
- the transformation of functions
Think of real-world examples and what the graphs look like for each of these.

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