1.？ Classification by definition?

2.？ According to positive and negative classification

3.？ Tip:?

(1) Infinitely cyclic decimals can be written as fractions, so they are rational numbers. ?

⑵ All positive numbers form a positive number set, all negative numbers form a negative number set, all integers form an integer set, and all rational numbers form a rational number set.

(3) Positive numbers and 0 are collectively referred to as non-negative numbers, and negative numbers and 0 are collectively referred to as non-positive numbers.

Second,? Definition of rational number

Rational number is a general term for integer (positive integer, 0, negative integer) and fraction. Positive integers and fractions are collectively referred to as positive rational numbers, and negative integers and fractions are collectively referred to as negative rational numbers. Therefore, the number of rational number sets can be divided into positive rational numbers, negative rational numbers and zero. Since any integer or fraction can be converted into a cyclic decimal, and vice versa, every cyclic decimal can also be converted into an integer or fraction, so a rational number can also be defined as a cyclic decimal.