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How to express a set by description?
Write the general symbols and range of values (or changes) of the elements in this set with braces, then draw a vertical line, and write the * * * same characteristics of the elements in this set after the vertical line.

Definition of description: often used to represent an infinite set. The public and private attributes of elements in a collection are described by words, symbols or expressions, and are described by? Wearing braces.

This method of representing a set is called description. {x|P}(x is the general form of the elements of this set, and p is the * * * same property of the elements of this set) For example, a set composed of positive real numbers less than π is expressed as {x | 0.

Extended data

1. Write clearly the symbols of the elements represented by this set. For example, the set {x ∈ r | x

2. All descriptions should be written in curly braces. For example, {x ∈ z | x = 2k}, k∈Z, this expression does not meet the requirements, and k ∈ z should also be written as curly braces, that is, {x ∈ z | x = 2k, k ∈ z.

3. In general, if the left element of the vertical line in the set belongs to the real number set, it can be omitted. For example, the real number solution set of equation x2-2x+ 1 = 0 can be expressed as {x ∈ r | x2-2x+ 1 = 0} or written as {x | x2-2x+6540}.

4. In some cases, the representative element of a set is just a symbol, which has nothing to do with whether it is X or Y; For example: {x ∈ r | x

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