Dividing by a number is equal to multiplying the reciprocal of this number; Divide two numbers, the same sign is positive, the different sign is negative, and divide by the absolute value. Divide 0 by any number that is not equal to 0 to get 0.

Data expansion:

Rational number is the collective name of integer (positive integer, 0, negative integer) and fraction, and it is the set of integer and fraction. Integers can also be regarded as fractions with a denominator of 1 Real numbers that are not rational numbers are called irrational numbers, that is, the fractional part of irrational numbers is infinite cyclic numbers.

It is one of the important contents in the field of number and algebra, and it is widely used in real life. It is the basis for continuing to learn real numbers, algebraic expressions, equations, inequalities, rectangular coordinate systems, functions, statistics and other mathematical contents and related disciplines.

The set of rational numbers can be represented by the capital black orthographic symbol Q, but Q does not represent rational numbers. The set of rational numbers and rational numbers are two different concepts. The set of rational numbers is the set of all rational numbers, and rational numbers are all elements in the set of rational numbers.

Understanding of rational numbers;

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.

The set of rational numbers is an extension of the set of integers. In the set of rational numbers, the four operations of addition, subtraction, multiplication and division (divisor is not zero) are unimpeded. Provisions on the order of magnitude of rational numbers A and B: If a-b is a positive rational number, it is said that when A is greater than B or B is less than A, it is marked as A >；; B or b < a. Any two unequal rational numbers can compare sizes.

An important difference between rational number set and integer set is that rational number set is dense while integer set is dense. After arranging rational numbers in order of size, there must be other rational numbers between any two rational numbers, which is density. Integer sets do not have this feature, so there are no other integers between two adjacent integers.

Rational numbers are compact subsets of real numbers: every real number has a rational number that is arbitrarily close. A related property is that only rational numbers can be transformed into finite continued fractions. Rational numbers have an ordered topology according to their sequences. Rational number is a (dense) subset of real number, so it also has subspace topology.