Positive numbers are usually preceded by a "+"symbol, which can usually be omitted. On the number axis, all positive numbers are on the right side of 0. Negative numbers are on the number axis, and all negative numbers are on the left of 0.
The plus sign before a positive number equals the absolute value of the positive number and the positive number itself. The minus sign before a negative number is equal to the absolute value of the negative number.
Extended data
The origin of positive and negative numbers
According to historical records, as early as two thousand years ago, China had the concepts of positive and negative numbers.
Liu Hui, a scholar in the Three Kingdoms period, made great contributions to the establishment of the concept of negative numbers. Liu Hui first gave the definitions of positive numbers and negative numbers. He said: "Today's gains and losses are the opposite, and positive and negative numbers should be named." In other words, in the process of calculation, positive numbers and negative numbers should be used to distinguish.
Liu Hui gave the method of distinguishing positive and negative numbers for the first time. He said: "two gains and one loss are opposites, and one positive and one negative should be corrected;" The front is red and the back is black; Otherwise, it will be different if it is tilted. " In other words, the number of the red stick pendulum represents a positive number, and the number of the black stick pendulum represents a negative number; You can also use a stick with an oblique pendulum to represent negative numbers, and a stick with a positive pendulum to represent positive numbers.
In China's famous ancient mathematical monograph "Nine Chapters of Arithmetic" (written in the first century AD), the law of addition and subtraction of positive and negative numbers was put forward for the first time: "Positive and negative numbers say: the same name is divided, different names are beneficial, positive and negative; Its synonyms are divided, and the same name is beneficial, without positive, negative and negative points. "
In the present words: "the addition and subtraction of positive and negative numbers is: the subtraction of two numbers with the same sign equals the subtraction of their absolute values, and the subtraction of two numbers with different signs equals the addition of their absolute values." Zero minus a positive number is a negative number, and zero minus a positive number. The addition of two numbers with different signs equals the subtraction of their absolute values, and the addition of two numbers with the same sign equals the addition of their absolute values. Zero plus positive equals positive, zero plus negative equals negative.