A **function** It is a correspondence between two sets of elements, which occurs when each of the elements of the domain set is related to a single element of the range set. Where the elements of the domain set are never repeated.

There are different types of functions such as: **injectives**, **surjectives** y **bijectives**.

**Injective function**

A function is **injective** when each element in the domain has only one element in the range.

Recall that the domain and range of a function are graphically represented in the Cartesian system as the x-axis and the y-axis, the union of each element of the domain with the elements of the range graphically represent a point (x, y) (domain, range) . Joining these points we will have the graphic representation of a function. To graphically check whether a function is injective or not, lines are drawn parallel to the domain axis (the x axis). If they cut the function only at one point, then it is injective, otherwise (it cuts at more than one point) it is not. Example:

**Surjective function**

A function is **surjective** if each element in its range (y axis), at least one domain element (x axis) belongs to it.

To know graphically if a function is surjective, we must draw lines parallel to the x-axis and observe if they cut the function at least one point. Example:

## **Bijective function **

It is that function that is **injective and surjective at the same time**Or, that is, each element of the domain has an element in the range and vice versa. From the previous examples the following graphs are bijective functions: