Re: [理工] [離散] 99中山資工

看板Grad-ProbAsk作者jameschou (DOG)時間14年前 (2011/02/27 23:56)推噓6(6推 0噓 2→)

留言8則, 6人參與討論串2/3 (看更多)

※ 引述《annheilong (方格子)》之銘言： : 3. Find the coefficient of x^72 in (x^6 + X^7 + X^8 + ...)^10 (x^6 + x^7 + x^8 + ...)^10 = x^60 * (1 + x + x^2 + ... )^10 所以相當於求 (1 + x + x^2 + ... )^10 中 x^12項係數 (1 + x + x^2 + ... )^10 = (1/1-x)^10 = (1-x)^(-10) ∞ -10 = Σ C *(-x)^i i=0 i -10 21 代入 i=12可得 x^12項係數為 C = C 12 12 : 4. Let A be a set with |A| = n, and let R be a binary : relation on A that is reflexive and antisymmetric. : (a) What is the maximum value for |R| : (b) How many antisymmetric relations can have this size? (a) 1+2+3+...+n = n(n+1)/2 所以最多 n(n+1)/2 個 (b) n(n-1)/2 2 (就是二的1+2+...+(n-1)次方種) 這題不確定對不對.. 我英文不太好不是很確定題意= =" -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.113.139.82

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daniel770624

02/28 17:04, , 1^F

02/28 17:04, 1^F

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annheilong

02/28 17:25, , 2^F

02/28 17:25, 2^F

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kai5566

02/28 19:24, , 3^F

02/28 19:24, 3^F