Expert: Chen Min - 12/24/2008

Question
please tell me what is function?

Answer
Function is like an answering machine.You input a value for the required independent variable, and the function will work out the value of the dependent variable.

E.g: y = x + 4 is a function, as when you type in x = 6, you get y = 10.
z = x + y + 2 is also a function, as when you type in x and y, you get the value of z.

Here, what you type is independent variables, which is controlled by you, and the result, dependent variable is controlled by your input.the dependent variable is therefore a function of independent variable(s).

To make things more explicit, we use f(x) to denote function for x, f(x,y) for function of x and y. f(x) and g(x) will be different functions, e.g. f(x) might be x+1 while g(x)is 2x + 8.

Many thingd develop from functions, like Caucasian's coordinates, calculus, functional geometry, complex plane.....etc.