The addition rule of rational numbers: add two numbers with the same sign, take the same sign and add the absolute values; Two numbers with opposite signs are added, and when the absolute values are equal, the sum is zero; When the absolute values are not equal, take the sign of the number with larger absolute value and subtract the number with smaller absolute value from the number with larger absolute value; Adding a number to zero still gets this number. Law of rational number subtraction: subtracting a number is equal to adding the reciprocal of this number.

Rational number arithmetic

The addition of 1 rational numbers also has commutative law and associative law (the same as integers), which are expressed in letters: commutative law: a+b = b+a.

When two numbers are added, the positions of the addend are exchanged and the sum is unchanged. Law of association: a+b+c=(a+b)+c=a+(b+c). Add three numbers, first add the first two numbers, or add the last two numbers first, and the sum remains the same.

Rule of rational number subtraction: subtracting a number is equal to adding the reciprocal of this number. Among them: two changes: subtraction becomes addition, and subtraction becomes its inverse. Invariant: The minuend is invariant. Can be expressed as:

a-b=a+(-b).