1. additive commutative law: Two numbers are added, the position of the addend is exchanged, and the sum is unchanged. Expressed in letters as a+b = b+a.

2. The law of addition and association: When three numbers are added, the first two numbers are added first, or the last two numbers are added first, and the sum is unchanged. Expressed in letters as (a+b)+c=a+(b+c).

Data expansion:

Addition is one of the four basic operations, which refers to the calculation of combining two or more numbers and quantities into one number and quantity. The symbol of addition is the plus sign "+". Connect items with a plus sign when adding.

Introduction to addition:

Addition (usually indicated by the plus sign "+") is one of the four basic arithmetic operations, and the others are subtraction, multiplication and division. For example, in the picture below, * * * has a combination of three apples and two apples, and * * * counts as five apples. This observation is equivalent to the mathematical expression "3+2=5", that is, "3 plus 2 equals 5".

In addition to calculating fruits, you can also calculate other physical objects. Using system generalization, addition can also be defined on more abstract quantities, such as integers, rational numbers, real numbers and complex numbers, and other abstract objects, such as vectors and matrices. In arithmetic, the addition rules involving fractions and negative numbers are designed.

Addition has several important properties. It is interchangeable, which means that the order is not important, it is interrelated, which means that when more than two numbers are added, the order in which the addition is performed is not important. Repeatedly adding 1 is the same as counting; Adding 0 will not change the result. Addition also follows related operations such as subtraction and multiplication.

Addition is one of the simplest digital tasks. The most basic addition: 1+ 1 five-month-old babies and even other animal species can be counted. In primary education, students are taught to calculate the superposition of decimal numbers, starting with one digit, and gradually solving the more difficult number calculation.

The essence of addition:

It is exactly the same thing, that is, the repetition or accumulation of similar things, which is the beginning of numerical operation. Different kinds, such as an apple and an orange, can only be equal to two fruits, so there is a relationship between classification and classification. Subtraction is the inverse operation of addition; Multiplication is a special form of addition; Division is the inverse of multiplication.

Power is a simple form of multiplication; The root is the inverse operation of power; Logarithm is the law of finding power term; Derivative is developed from logarithm; Then differential and integral. The development of digital operation is a more special situation and a more repetitive law.