Multiplication and distribution law: a(b+c)=ab+ac.

Law of multiplicative association: ab+ac=a(b+c)

Multiplicative commutative law: ab=ba

2, the law of addition:

Addition has no distribution law.

Additive associative law: (a+b)+c=a+(b+c)

Additive commutative law: A+B = B+A.

Extended data

1. In addition calculation, when some addends can be added to form integer ten, integer hundred and integer thousand, the addition algorithm can make the calculation simple.

Formula: Look at the calculation carefully and consider the addend is the key. Whole ten, whole hundred and whole thousand are easier to combine. Law of Exchange Remember that the sum of exchange positions is constant. The law of combination is widely used, and it is easier to round the addend.

2. In the multiplication calculation, when the product of two multipliers is exactly integer ten, integer hundred and integer thousand, the multiplication algorithm can make the calculation simple.

By using the method of decomposition, a multiplier is decomposed into the form of multiplication of several numbers, so that the product of this multiplier and other multipliers is rounded up.

The law of multiplication and distribution should pay special attention to the two words in "the sum of two numbers is multiplied by a number, which can be multiplied first and then added"

note:

1、? Be sure to multiply the number outside the brackets by the two numbers inside the brackets, and then add the products. The distribution law of multiplication to subtraction is that the numbers outside brackets are multiplied by the two numbers in brackets respectively, and then the product is subtracted.

2、? The same factor in two products can only be written once.