作者s987692 (阿诚)
看板Grad-ProbAsk
标题Re: [问题] 离散
时间Mon Mar 16 23:10:27 2009
※ 引述《ooopppeeennn (open)》之铭言：
: In how many ways can 200 identical chairs be divided among
: four conference rooms such that each room will have 20 or
: 40 or 60 or 80 or 100 chairs?
A(X)=(x^20+x^40+x^60+x^80+x^100)^4
= x^80(1+x^20+x^40+x^40+x^80)^4
= X^80 [1-x^100/1-x^20]^4
= x^80 [1-4x^100+6x^200-4x^300+x^400] (1-x^20)^-4
= [1-4x^100+6x^200-4x^300+x^400] C(4+r-1,r)x^100+r
取x^200 之系数
c(103,100)-4(3,0)
应该是这样吧 希望没算错
--
※ 发信站: 批踢踢实业坊(ptt.cc)
◆ From: 114.42.200.172
1F：推 ooopppeeennn:请问一下c(103,100)-????? 後面那个有打错吗?? 03/17 01:01
2F：→ s987692:少打了一个C SRY 03/17 01:31