Positive number: a real number greater than 0, such as 5.2.
Non-negative number: a real number that is not negative, positive and 0.
Non-positive number: Non-positive real number, which refers to negative number and 0.
Note that 0 is neither a positive number nor a negative number, although it is regarded as a positive number in some calculations.
Negative integers can be regarded as an extension of natural numbers, which makes the equation x? Y = z is meaningful to any X and Y. Relatively speaking, the set of other numbers is obtained by gradually expanding natural numbers.
Negative numbers are very useful when representing values less than 0. For example, in accounting, it can be used to represent liabilities, usually in red (without negative sign or brackets), so it is also called "deficit".
Mathematicians in China have known the concepts of negative numbers and zero since the 4th century BC. [1] The Nine Chapters of Arithmetic in a.d. 1 century said, "The art of pros and cons is: the same name is divided, the different names are beneficial, there is no negative, and the negative is not positive. Its synonyms are divided, the same name is beneficial, and there is no positive or negative. " Subtraction: When you meet numbers with the same sign, subtract their values; when you meet numbers with different signs, add their values. The difference between zero MINUS positive numbers is negative, and the difference between zero MINUS positive numbers is positive. " ) The concept of "Buru" in the above text is usually considered as zero by mathematical historians. (For the full text, see Chapter 9 of Wikipedia Arithmetic. )
The earliest use of negative numbers in western mathematics is an Indian mathematical document written by Brahmagupta in BrahmaSphuta-Sidd'hanta in 628. It seems to indicate negative assets or debts. To a large extent, European mathematicians did not accept the probability of negative numbers until17th century.