A function represents the relationship of two variables in which one variable depends on, or is a function of the other variable.
In the case of a simple graph of x and y values, the value of y depends on the value of x, or is a function of x; that means tha y = f(x).
Here we review a number of different forms of f(x) and what it means to evaluate and plot the limit of f(x).
Functions and limits