Four operations refer to four operations: addition, subtraction, multiplication and division. Four operations are the important content of primary school mathematics and the basis of learning other related knowledge.
Additive related properties:
1, additive commutative law: a+b = b+a.
For example: 8+ 1= 1+8=9
100+2=2+ 100= 102
2. Additive associative law: a+b+c=a+(b+c)
For example: 7+4+1= 7+(4+1) = (7+4)+1=12.
10-5+2=( 10+2)-5=7
The associative law refers to the binary operation on a given set S. If there is an additive associative law a+b+c=(a+b)+c=a+(b+c) or a multiplicative associative law ax(bxc) = (axb)xc in S, the operation is said to satisfy the associative law.
Test and analysis: From the nature of N(x), we can know that when x is odd, the largest odd factor of x is obviously itself. So N(x)=x, so we can decompose and calculate the s