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Mathematical set description method
First, natural language:

Features: The scenery is described in the form of text narration.

Applicable object: a collection of concrete or abstract objects with certain properties.

Second, the description method:

Features: A set is represented by the same features of the elements contained in the * * * set.

Applicable object: the elements in the collection have the same characteristics.

Third, the enumeration method:

Features: when the number of elements is limited, the elements of the set are listed one by one; When the number of elements is infinite, their changing rules are expressed.

Applicable object: the number of elements is more or less, and there is an obvious set of rules between elements.

Extended data:

Four representations of a set:

1, enumeration method

Enumeration is a method of enumerating the elements of a collection one by one. For example, there are four seasons in a year, which can be represented by a collection {spring, summer, autumn and winter}.

Enumeration also includes the case that the elements of a set can not be enumerated one by one, but their changing rules can be expressed. For example, the set of positive integers N+ can be expressed as n+= {1, 2, 3, ..., n, ...}

Step 2 describe the method

The description method is in the form of {representing element | satisfying attribute}. Let the set S consist of all elements with a certain property p, then the set can be expressed by describing the common properties of the elements in the set: S={x|P(x)}.

3. Wayne diagram method (Webster diagram method)

It is a method of representing a set with a set of points on a two-dimensional plane. A set is generally represented by a rectangle or a circle on a plane, which is an intuitive graphical representation of the set.

4. Symbolic method

Some sets can be represented by some special symbols, such as:

N: non-negative integer set or natural number set {0, 1, 2, 3, …}

N* or N+: positive integer set {1, 2,3, …}

Z: integer set {…,-1, 0, 1, …}

Q: Rational number set

Q+: Set of Positive Rational Numbers

Q-: set of negative rational numbers

R: set of real numbers (including rational numbers and irrational numbers)

R+: positive real number set

R-: negative real number set

C: complex set

: empty set (a set without any elements)

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