2. Multiplicative commutative law: a× b = b× a;

3. Additive associative law: A+B+C = (A+B)+C = A+(B+C);

4. Multiplicative associative law: (a× b )× c = a× (b× c);

5. Multiplicative distribution law: a× (b+c) = a× b+a× c;

6. Left distribution law: CX (a+b) = (cxa)+(cxb);

7. Right distribution method: (a+b)xc = (axc)+(bxc).

In the addition operation of two numbers, according to the calculation order from left to right, two addends are added, the positions of addends are exchanged, and the sum is unchanged. For example:

Letters: a+b = b+aa+c = c+a.

Numbers:1+2 = 2+116+30 = 30+16.

Extended data:

Commutative law is a property of binary operation, which means that in an expression containing more than two commutative operators, as long as the operators have not changed, the order of their operations will not affect the calculated value.

Addition, subtraction, multiplication and division are called four operations. Among them, addition and subtraction are called first-order operations; Multiplication and division are called secondary operations.

Calculation order:

(1) at the same level, calculated from left to right;

(2) When performing secondary operation, multiply first, then divide, and then add and subtract.

(3) When there are brackets, count the inside of brackets first, and then count the outside of brackets;

(4) When there are multiple brackets, count the brackets first, then the brackets inside, and finally the brackets outside.

(5) If there is power, calculate the power first.

(6) When performing mixed operation, first calculate the numbers in parentheses, and the parentheses are from small to large. If there is a power, calculate the power first, and then from high to low.

In the formula calculation with only multiplication, the calculation is generally carried out from left to right.

Baidu Encyclopedia-additive commutative law

Baidu Encyclopedia-Multiplication method of substitution