问答题(1947年武汉大学

试求(1+2x+10x2)10之展开式中x5之系数.

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讨论

已知多项式(x-1)3+(x+1)4=x4+a1 x3+a2 x2+a3 x+a4,则a1=________,a2+a3+a4=________.

数码a1,a2,a3,⋯,a2006中有奇数个9的2007位十进制数的个数为【 】.

甲乙丙丁戊5名同学站成一排参加文艺汇演,若甲不站在两端,丙和丁相邻的不同排列方式有【 】

已知多项式(x+2)(x-1)4=a0+a1 x+a2 x2+a3 x3+a4 x4+a5 x5,则a2=__________,a1+a2+a3+a4+a5=___________.

二项式(3+x)n的展开式中,x2项的系数是常数项的5倍,则n=________.

The Bank of Oslo issues two types of coin:aluminium(denoted A) and bronze(denoted B). Marianne has n aluminium coins and n bronze coins, arranged in a row in some arbitrary initial order.A chain is any subsequence of consecutive coins of the same type.Given a fixed positive integer k<2n, Marianne repeatedly performs the following operation:she identifies the longest chain containing the kth coin from the left and moves all coins in that chain to the left end of the row.For example, if n = 4 and k=4 the process starting from the ordering AABBBABA would beAABBBABA→BBBAAABA→AAABBBBA→BBBBAAAA.Find all pairs (n, k) with 1 ≤ k ≤2n such that for every initial ordering at some moment during the process,the leftmost n coins will all be of the same type. 译文:奥斯陆银行发行了两种货币:铝币(记为A)和铜币(记为B).玛丽安有n枚铝币和n枚铜币,以任意初始方式排成一排。定义一条链为任意由相同类型货币构成的连续子列。给定正整数k<2n,玛丽安重复地进行如下操作:她找出包含(从左到右)第k枚硬币的最长链,然后把该链中所有货币移到序列最左端。例如,n=4,k=4时,对于初始序列 AABBBABA,过程如下:AABBBABA→BBBAAABA→AAABBBBA→BBBBAAAA.求所有满足1≤k≤2n的数组(n,k),使得对任意初始序列,都可以在有限次操作内使左端为n枚相同的货币。

(x2-1/2x)9展开式中x9的系数是__________.

有 0,1,2,3,4,5,6,7 八个数字,可组成小于 10000 之数字有几?

的展开式中 x3y3 的系数为【 】

(x2 + 2/x)6 的展开式中常数项是 ______(用数字作答).