Unless otherwise specified, concepts and properties are integers, and the letters used also represent integers.
Definition: let a and b be given numbers, and b≠0. If there is an integer C that makes a=bc, then B is called divisible by A, that is, b|a, where B is a divisor (factor) of A and A is a multiple of B. If there is no integer C, then B cannot be divisible by A. ..
What is natural number set? Natural number set is a set of all non-negative integers (in the past textbooks, it was generally considered that zero is not a natural number, but the regulation of 2 1 century shows that zero is indeed a natural number, and the reason for the correction is for convenience and conciseness), and it is often represented by n. There are infinite natural numbers.
Definition of real numbers Real numbers can be divided into rational numbers and irrational numbers, or algebraic numbers and transcendental numbers, or positive real numbers, negative real numbers and zero. Rational numbers can be divided into integers and fractions, and integers can be divided into positive integers, zero and negative integers. Scores can be divided into positive scores and negative scores. Irrational numbers can be divided into positive irrational numbers and negative irrational numbers. A set of real numbers is usually represented by the letter r or r n, and r n represents an n-dimensional real number space. Real numbers are uncountable.