How to calculate the calculation process, mathematical arrangement and combination, and AC respectively
Here is an example. A(4，4)= 4x(4- 1)x(4-2)x(4-3)x(4-4+ 1)= 4x 1x2x3x 1 = 24 .
A(6，6)=6x5x4x3x2x 1=720。
A(6，4)=6！ /(6-4)! =(6x5x4x3x2x 1)/2=360
C(4，2)=A(4，2)/2！ = {[4x(4- 1)x(4-2)x(4-3)x(4-4+ 1)]
2! = 1x2