Matters needing attention in comprehensive calculation formula (four operations):

1. If there is only addition and subtraction or only multiplication and division, it is calculated from left to right. For example, 2+ 1- 1=2, first calculate the number of 2+ 1, and then subtract 1 from the number of 2+ 1.

2. If primary operation and secondary operation exist at the same time, the secondary operation is calculated first.

3. If there are primary, secondary and tertiary operations (i.e. power, root and logarithm operations) at the same time, first calculate the tertiary operation, and then calculate the other two levels.

4. If there are brackets, count the numbers in brackets first (no matter what level, count first).

5. The third level should be counted in brackets, and then the second and first levels should be counted.

Extended data

1, the nature of addition

Exchange law: a+b = b+a;

Law of association: A+B+C = A+(B+C);

2. The essence of subtraction

a-b-c = a-(b+ c)；

3. The essence of multiplication

Exchange law, ab = ba

Law of association, a (BC) = (AB) c;

Distribution law, a (b+c) = ab+AC;

4. Law of division

How many digits is the divisor? Look at the first few digits of the divisor first. If the first few digits are not divided enough, look at another one. Except the one to which they belong, all the vendors will write on it, which is not enough for a quotient of one and zero. The remainder is less than the divisor. If the quotient is decimal, the decimal point of the quotient should be aligned with that of the dividend. If the divisor is a decimal, it must be divided into integers and then calculated.

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