Re: [問題] 離散
※ 引述《ooopppeeennn (open)》之銘言：
: 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 之係數
c(103,100)-4(3,0)
應該是這樣吧 希望沒算錯
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