Sets {1, 2}, {1, 4, 7} have neither good nor bad number sets;

A number set is a set of numbers.

The elements in this set are different from those in other sets.

Extended data:

A set refers to a set of concrete or abstract objects with certain properties, called elements of a set, and a number set is a number set. The range of set is greater than that of number set, and number set is just one kind of set. What belongs to a number set must belong to a set, and what belongs to a set is not necessarily a number set.

Dataset type:

Some commonly used number sets in mathematics and their representations;

The set of all positive integers is called a positive integer set, and it is recorded as N*, z? Or n? ;

The set of all negative integers is called the set of negative integers, denoted as z? ;

The set composed of all nonnegative integers is called nonnegative integer set (or natural number set), and is denoted as n;

The set composed of all integers is called integer set, which is denoted as z;

The set of all rational numbers is called rational number set, and it is recorded as q;

The set composed of all real numbers is called real number set, which is denoted as r;

The set composed of all imaginary numbers is called imaginary number set, which is denoted as I;

The set of complex numbers composed of all real numbers and imaginary numbers is called complex number set, and it is recorded as C.

The relationship between number set and number set;

1、N*？ n？ z？ q？ r？ c，

2、Z*=Z？ ∪Z？ ,

3, Q={m/n|m∈Z, n∈N*}={ decimal} = {cyclic decimal},

4、R∪I=C，

5、R*=R\{0}=R？ ∪R？ =(-∞,0)∪(0,+∞),

6、R=R？ ∪R？ ∨{ 0} = R * ∨{ 0 }={ decimal} = Q ∨{ irrational number} = {cyclic decimal} {acyclic decimal}.

Collection elements have the following properties:

1. Certainty: Every object can determine whether it is an element of a set. Without certainty, it cannot be a set. 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.

2. Relevance: Any two elements in the set are different objects.

3. Disorder: In a set, the state of each element is the same, and the elements are out of order. You can define an order relation on the set. After defining the order relation, you can sort the elements according to the order relation. But as far as the characteristics of the set itself are concerned, there is no necessary order between elements.

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