1, rational number addition and subtraction rules

(1) Add two numbers with the same sign, take the same sign, and add the absolute values.

(2) Add two numbers with different symbols, take the symbol with larger absolute value, and subtract the one with smaller absolute value from the one with larger absolute value.

(3) When a number is added to 0, the number is still obtained.

2. Arithmetic rules of rational number addition and subtraction

The commutative law of (1) addition: a+b = b+a.

(2) The associative law of addition: (a+b)+c=a+(b+c).

3, rational number multiplication rule

Subtracting a number is equal to adding the reciprocal of this number; That is, a-b=a+(-b).

4, rational number multiplication rule

(1) Multiply two numbers, the same sign is positive, the different sign is negative, and the absolute value is multiplied.

(2) Any number multiplied by zero gets zero.

(3) When several numbers are multiplied, one factor is zero and the product is zero; Each factor is not zero, and the sign of the product is determined by the number of negative factors.

5, rational number division rule

Dividing by a number is equal to multiplying the reciprocal of this number. (Note: Zero cannot be divided).