a=0，lal=0: a-0，lal = a； a≤0。 lal-a； lal- 1b 1 . a & lt； 0.b<0, and then

2. additive commutative law: A+B = B+A.

3. Additive associative law: (a+b)+c=a+(b+c)

4. subtraction rule: a-b=a+(-b)

5. Multiplicative commutative law: ab=ba

6. Good law: (ab)c=a(bc)

7. Division rule: a-b=a( 1-b) (b*0)

8. The circumference of a rectangle = (length +g× 2c = (a+b) x2.

9. The circumference of a square = side length ×4C=4a.

10. Rectangular area = length and width S=ab

1 1. square area = side length x side length s = a.a = a.

12. area of triangle = base x height =2 S=ahi2.

13. area of parallelogram = bottom x height S=ah.

14. Trapezoidal area = (upper bottom+lower bottom) x height =2 5=(a+b)h-2.

15. diameter = radius× 2d = 2r radius-diameter; 2r= d:2

16. The perimeter of the garden =πx diameter =πx radius x2 C=Td =2TT.

The above is the first mathematical formula compiled by Bian Xiao. I hope it will help you.