What are the two elements of a function?

The definition of function is usually divided into traditional definition and modern definition. The two definitions of functions are essentially the same, but the starting point of describing concepts is different. The traditional definition is from the perspective of movement change, and the modern definition is from the perspective of set and mapping.

brief introduction

First of all, we should understand that a function is the corresponding relationship between sets. Then, we should understand that there is more than one functional relationship between A and B, and finally, we should focus on understanding the three elements of the function.

The corresponding rules of functions are usually expressed by analytical expressions, but a large number of functional relationships can not be expressed by analytical expressions, but only by images, tables and other forms.