抛硬币问题.抛到第N次,那么n+1,n+2,n+3,n+4分别跟n-3,n-2,n-1,n的结果相同的概率是多少?也是等

证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n n≥3,n∈N,证明3的n-1次幂>2n-1 lim(n趋于无穷)[n(n+1)/2]/n方+3n的极限是多少? Sn=n(n+2)(n+4)的分项等于1/6[n(n+2)(n+4)(n+5)-(n-1)n(n+2)(n+4)]吗? [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 2^n/n*(n+1) 化简：1/(n+1)(n+2)+1/(n+2)(n+3)+1/(n+3)(n+4) (n+1)(n+2)/1 +(n+2)(n+3)/1 +(n+3)(n+4)/1 lim((5^n-4^(n-1))/((5^(n+1)+3^(n+2)) n→∞时的极限是多少? 化简(n+1)(n+2)(n+3) 1\n(n+3)+1\(n+3)(n+6)+1\(n+6)(n+9)=1\2 n+18 n为正整数,求n的值 如果,n是大于2的整数,计算1/(n-1)(n-2)+1/(n-2)(n-3)+1/(n-3)(n-4)+……+1/(n