Function

  A Function is a rule that takes certain numbers as inputs and 

assigns to each a definite output numbers.

    Domain : 

  The set of all input numbers are called the ' Domain' of the 

function.

    Range :

   The set of resulting output numbers are called the ' Range' of 

the function.

       

       Input is called the independent variable and Output is 

called  the dependent variable. 

       

       Example :

        y = f (x) = x^2 + 2

Here , y = output = dependent variable

               x = input = independent variable

     Domain = possible set of x

     Range = Possible set of y

In this function 

Domain = 0, -1, 1, 2, ... ... ... ..

Range = 2, 3, 3, 6 ... ...