① Understand the meaning of set and the "subordinate" relationship between elements and set through examples.

② We can choose natural language, graphic language and assembly language (enumeration or description) to describe different specific problems and feel the significance and function of assembly language.

(2) the basic relationship between sets

① By understanding the meaning of inclusion and equality between sets, we can identify a subset of a given set.

② Understand the meaning of complete works and empty sets in specific situations.

Finite set: A set containing a finite number of elements.

Infinite set: A set containing infinite elements.

Empty set: An example of a set without any elements: {x | x2 =-5}

Extended data:

Each object can determine whether it is an element in the collection. Without certainty, there will be no trap. For example, "tall classmates" and "small numbers" cannot form a set. This property is mainly used to judge whether a set can constitute a set.

Any two elements in a collection are different objects. If written as {1, 1, 2}, it is equivalent to {1, 2}. Being different from each other makes the elements in the collection not repeat. When two identical objects are in the same set, they can only be counted as an element of this set.

Disorder: {a, b, c}{c, b, a} are the same set.

The purity of a set is represented by an example. Set a = {x | x

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