Function (mathematics) - Simple English Wikipedia, the free encyclopedia

# Function (mathematics)

### From Simple English Wikipedia, the free encyclopedia

A function is a very important thing in mathematics. It is a rule that tells you what to do to an object in order to get a different object.

Functions are usually written as f(x). The f is short for function. f(x) is said: "function of x" or "f (eff) of x", for short.

It is sometimes said that f(x) is the image of x, and x is the pre-image of f(x). Also, it is said that the object x is transformed or mapped into f(x).

## [edit] Example

Here is an example of how functions work:
f(x) = x + 1 is a formula for a function. You are doing something to x that will make it a different number. In this example, you are adding 1 to the unknown number x. If you set x = 4, the function becomes f(4) = 4 + 1. This means that f(x) = 5 when x equals 4.

Many functions are more complex than this example but the pattern is always the same. For every input, x, you get a result, f(x).

## [edit] Types of functions

| The English used in this article may not be easy for everybody to understand. You can help Wikipedia by making this page or section simpler.

There are other functions, like trigonometric functions. In mathematical language, a function can be defined as a map from a non-empty set (called a domain) to a non-empty set (called a co-domain) such that for every element in the domain there is a corresponding unique element in the co-domain.

There are several basics types of functions:

- constant functions: all elements in the domain go to some fixed element in the co-domain
- injective functions: any two different elements are transformed into different ones
- surjective functions: all elements in the co-domain have a pre-image
- bijective functions: if it is both injective and surjective

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Categories: Complex pages | Mathematics

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