ֶ壬㷽ֻһ֣ǷֶĶַ㡣ǰmQnmnΪȻcļ㷽ʽο
1ACô
A(n,m)=n×n-1.n-m+1=n!/n-m!(nΪ±,mΪϱ,ͬ)
C(n,m)=P(n,m)/P(m,m)=n!/m!n-m!
A(4,2)=4!/2!=4*3=12
C(4,2)=4!/(2!*2!)=4*3/(2*1)=6
A32УC32
A32326
A636*5*4
ǴӴʼ˺ǸʾжٸA727*6*2λA52=5*4
ôC32ǻҪһC32A32ٳA22
C53A53A33
2ϵĶ弰㹫ʽ
ϵĶ֡ǰmQn
ٴnͬԪУȡmԪزһ飬nͬԪȡmԪصһϡ
ڴnͬԪУȡmԪصϵĸnͬԪȡmԪص
ⶨ壺4ɫУȡ2ɫγɶϡ
⣺C(4,2)=A(4,2)/2!={[4x(4-1)x(4-2)x(4-3)x(4-4+1)]/[2x(2-1)x(2-2+1)]}/[2x(2-1)x(2-2+1)]=[(4x3x2x1)/2]/2=6
Ƽ
߿ѧ֪ʶ
ѧȲʽ
¸߿Ѷ߿ߡǰ־Ը¼ȡߵ
߿ʱߵȫҪڵ
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