With a formula such as you will find exactly one value for for every value of . In that case, is a function of with function rule .
When you are given a function, you can compute a table and draw the corresponding
graph. The values of the input variable are found on the horizontal axis, the -axis.
The results are called function values.
is the function value if . Function values are found on the -axis.
You also find the expression being used for . then is a function of that is given the name .
In contextual situations you often use letters that have some connection to the meaning or name of the variable. For time you use , for length you use , for volume you use , for velocity you use , for power you use , etc. Your graphing calculator is set to use X as the standard input variable, and Y as the standard function value.
The zeros or roots of a function are those input values that give you a function value of . For the function above these are the -values for which:
In this case these values are , and .
The corresponding x-intersects are , and .