2. As long as the elements that make up two sets are the same, they are said to be equal. ?

3. Common set: positive integer set: *N or n, integer set: z, rational number set: q, real number set: r.

4. Representation methods of sets: enumeration method and description method.

5. For two sets A and B, if any element in set A is an element in set B, set A is said to be a subset of set B. ..

6. A set without any elements is called an empty set.

7. If set A contains n elements, set A has n2 subsets.

8. Let A and B be nonempty number sets. If any number X in set A has a unique number xf corresponding to it according to a certain correspondence F, it is called BAf: a function from set A to set B..

9. The constituent elements of a function are: definition domain, correspondence domain and value domain. Two functions are said to be equal if their domains are the same and their corresponding relationships are the same.

10, there are three ways to express functions: analytical method, image method and list method.