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Positive and negative numbers are a way to express numerical relations, reflecting the differences in quantity and direction of things described. Simply put, a positive number means increase, growth and surplus, and a negative number means decrease, decrease and loss.

In mathematics, a positive number means a number greater than zero and a negative number means a number less than zero. On the number axis, the center is zero, the right side is positive, and the left side is negative. When a number is located on the right side of the number axis, its absolute value is larger; On the contrary, the farther to the left, the greater the absolute value.

In real life, we often have to deal with positive and negative numbers. For example, the symbol of the temperature value indicates how much the temperature is higher or lower than the standard temperature, the symbol of the account balance indicates how much the account balance is overspent or surplus, and the symbol of the company's profit and loss indicates how much the company gains or loses.

Therefore, the significance of positive and negative numbers is that they can help us describe the increase and decrease, direction and relationship between numbers. By using positive and negative numbers, people can describe the change of numerical values more accurately, which is convenient for the transfer and understanding of knowledge and the solution of some practical problems.

In mathematics, positive numbers and negative numbers can also be added, subtracted, multiplied and divided by signed numbers. For example, adding two positive numbers will get a larger positive number, and adding two negative numbers will get a smaller negative number. The product of multiplication of positive and negative numbers also follows certain laws, for example, a positive number and a negative number are multiplied to get a negative number, and two positive numbers or two negative numbers are multiplied to get a positive number.

Positive numbers and negative numbers also have important applications in physics. In mechanics, the direction and magnitude of the resultant force depend on the direction and magnitude of each force. If an object is subjected to multiple forces, some of which point in the positive direction and some point in the negative direction, we need to calculate the direction and magnitude of the resultant force by positive and negative addition and subtraction.

In computer science, positive and negative numbers are the basis of two's complement representation. The computer uses binary to represent numerical values, where one bit represents the sign bit, 0 represents a positive number, and 1 represents a negative number. When a computer processes a negative number, it will convert it into a complement form, that is, add 1 to the complement of its absolute value, so that it can be calculated by addition and subtraction.