The same class or the same thing or the same behavior, for example, the students in grade three are a collection, because the boys in grade three are also a collection, and a large collection can contain many small collections.
A representation of a set.
1. enumeration: the method of enumerating the elements of a collection one by one and enclosing them with braces "{}" is called enumeration.
2. Description method:
Definition: The method of representing a set with the * * * same characteristics of the elements contained in the set is called descriptive method.
Writing: Write the general symbols and the range of values (or changes) of the elements in this set with curly braces, then draw a vertical line, and write the * * * same characteristics of the elements in this set after the vertical line.
3. Graphical method, also called Venn diagram.
4. Interval representation: used to represent continuous number sets. A chapter on the three elements of function will appear in the textbook.