## NEKG33 Mathematical methods for economists

## Chapter 13 : Day 13: Functions

### By Lund University

You have been working with functions since sixth grade (or thereabouts). Let's learn what a function really is!

## Functions in general

In the first section we study the general concept of a function. A function is a rule that for each element in the domain assigns an element in the codomain. We then focus on real-valued functions of one real variable and look at graphs of such functions. Next, we investigate what happens to the graph of a function when we make changes, such as multiplying the function by a scalar. Finally we look at the definitions of increasing and decreasing functions and the strict versions of these concepts.

#### Introduction to functions

#### Natural domain

#### The graph of a function

#### The sum, product, difference and ratio of two functions

#### Shifting graphs

#### Injective, surjective and bijective functions

## Functions in general: Problems

Exercises on functions