n等於多少
回答 (7)
2010-03-20 10:20 pm
✔ 最佳答案
剩餘定理若C(n,k)=C(n,r)
則(1) k=r 或(2) n=k+r
(1)7不等於4
(2)
2n+1=7+4=11
2n=10
n=5
C(n,n-3)=C(5,5-3)=C(5,2)=(5*4)/(2*1)=10
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參考: 龍騰數學
2010-03-20 8:13 pm
你的C是排列組合的C嗎?
所以原題是
C(2n+1，7)=C(2n+1，4)
求C(n，n-3)
是嗎
所以原題是
C(2n+1，7)=C(2n+1，4)
求C(n，n-3)
是嗎
2010-03-20 6:47 pm
這是一條有關「組合」的數。
C(2n + 1, 7) = C(2n + 1, 4)
(2n + 1)!/[(2n - 6)!7!] = (2n + 1)!/[(2n - 3)!4!]
(2n - 6)!7! = (2n - 3)!4!
7 * 6 * 5 = (2n - 3)(2n - 4)(2n - 5)
4n³ - 24n²+ 47n - 135 = 0
(n - 5)(4n²- 4n + 27) = 0
n = 5 ...... (答)
C(n, n - 3)
= C(5, 2)
= 5!/(3!2!)
= 10 ...... (答)
C(2n + 1, 7) = C(2n + 1, 4)
(2n + 1)!/[(2n - 6)!7!] = (2n + 1)!/[(2n - 3)!4!]
(2n - 6)!7! = (2n - 3)!4!
7 * 6 * 5 = (2n - 3)(2n - 4)(2n - 5)
4n³ - 24n²+ 47n - 135 = 0
(n - 5)(4n²- 4n + 27) = 0
n = 5 ...... (答)
C(n, n - 3)
= C(5, 2)
= 5!/(3!2!)
= 10 ...... (答)
參考: micatkie
2010-03-20 6:06 pm
這是機率, 不是解方程式
2010-03-20 6:03 pm
將牠展開後為:
2nC+17C=2nC+14C
17C=14C
C=0
所以C=0代入式子:
0(n n-3)=0
空格為0
2nC+17C=2nC+14C
17C=14C
C=0
所以C=0代入式子:
0(n n-3)=0
空格為0
2010-03-20 6:02 pm
7+4=2n+1……………(C(n,k)=C(n,n-k)=>k+(n-k)=n)
=>n=5
C(n n-3)= C(5, 2)=10
=>n=5
C(n n-3)= C(5, 2)=10
2010-03-20 5:53 pm
經過計算機計算過後
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