Variables
A variable is a symbol used to represent one or more numbers. The numbers are called the values of the variable .
Example :
My sister Emily is years older than me, so:
When I was , she was .
When I was , she was .
When I was ( Dan's age ), she was
( Dan's age ) + 4 .
We can say ( Emily's age ) = ( Dan's age ) + 4 ,
or simply , where = Emily's age, and = Dan's age.
The quantities "Dan's age", "Emily's age", " ", and " " are variables because they can represent many different numbers.
In a functional relationship, we say the dependent variable (usually or ( )) is a function of the independent variable (usually ). It is possible for a function to have more than one independent variable.
Example :
The function gives the perimeter of a square with side length . Here is the dependent variable, and is the independent variable.
Usually, when graphing a function, the independent variable is graphed on the horizontal axis, and the dependent variable on the vertical axis.