Function: is a relationship between two attributes or quantities and can be represented by a formula,
a table of paired values, a graph or a relational statement (word problem).

Also a function is a rule which takes certain values as inputs and assigns to each input exactly one output.
The output is a function of the input or the output (usually the y-variable) is dependent on the input
(usually the x-variable). The output is called the dependent variable and the input is called the independent variable.

When we use a function to describe actual situation, the function is called a mathematical model.

Examples of all 4 forms of a function:
 

Word: Function Form Temperature in degrees Fahrenheit is converted to degree Celsius by subtracting 32 and multiply by	Formula: Function Form
Table: Function Form     Fahrenheit Celsius -13 -25 -32 0                                212                             100	Graph: Function Form

Test if a graph is a function: Vertical line test:

A vertical line drawn on a graph is a function (the graph) if it intersects the graph at only one point or place.

Examples of Functions Used in this Course

Examples of graphs that are not functions ( since more than one values for output variables for
some values of input variable)