Formula for adding and subtracting brackets: the key to adding brackets is to look at the symbols, and there is a plus sign in front of the brackets, and the brackets remain unchanged; There is a minus sign in front of the brackets, which will change when the brackets are deleted and added.

The formula for removing brackets by multiplication and division: there is a division symbol in front of the brackets, and the symbol is changed when the brackets are removed; There is a multiplication symbol in front of the parentheses, and the invariant symbol is removed. The rule of removing brackets is based on the laws of multiplication and distribution. The symbol before brackets is the basis for whether the items in brackets change their symbols after removing brackets.

Hybrid algorithm

(1) If there is only addition and subtraction in the formula, it will be calculated in turn; Only multiplication and division are calculated in turn.

(2) There are both addition and subtraction and multiplication in the formula. Multiplication first, then addition and subtraction.

(3) There are both addition and subtraction and division in the formula. Calculate division first, then add and subtract.

(4) The parts that are not involved in calculation in each step should be copied down with the same position and symbols to ensure that the equal sign is equal before and after.

(5) The function of parentheses in mixed operation is to change the operation order. Operation sequence of mixed operation with brackets: first calculate the inside of brackets, then calculate the outside of brackets.