A function of variable x is a rule f that assigns to each value of x aunique number f(x), called the value of the function at x. [We read "f(x)" as "f of x."] The variable x is called the independent variable. The set of values that the independent variable is allowed to assume is called the domain of the function.
The domain of a function may be explicityly specified as part of the definition of a function or it may be understood from context. The range of a function is the set of values that the function assumes.
The functions will usually be defined by algebraic formulas. For example, the domain of the function
f(x)=3x-1
consists of all real numbers x. This function is the rule that takes a number , multiplies it by 3, and then subtracts 1. If we specify a value of x , say x = 2, then we find the value of the function at 2 by substituting 2 for x in the formular:
f(2)=3(2)-1=5
NEXT: Exponentiation