Classification of four operations and simple operations

Knowledge point one:

1, the same level operation (including only addition and subtraction, or only multiplication and division), calculated from left to right.

2. The same operation includes both addition and subtraction and multiplication and division. Calculate multiplication and division first, then addition and subtraction.

3. In the mixed operation with parentheses, count the parentheses first, and then count the parentheses.

4, column comprehensive formula to solve practical problems, we must consider the application of parentheses.

5. Calculation related to 0 (a number adds 0 to get this number, a number subtracts 0 to get this number, a number multiplies 0 to get 0, and 0 cannot be divided.

Knowledge point 2: algorithm and simple operation

1, law of additive association: a+b+c=a+(b+c)

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

2. Multiplicative commutative law: a×b=b×c

The law of multiplicative association: a×b×c=a×(b×c)

Multiplication and distribution law: (a+b)×c=a×c+b×c

Inverse operation of multiplication and distribution law: a× c+b× c = (a+b )× c.