1/(2n-1)(2n+1）1/n（n+1）（n+2）

2^n/n*(n+1) 证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n 2n/（n+1）n! (n+2)!/(n+1)! [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 化简n分之n-1+n分之n-2+n分之n-3+.+n分之1 化简n分之n-1+n分之n-2+n分之n-3+.+n分之1 f(x)=e^x-x 求证(1/n)^n+(2/n)^n+...+(n/n)^n 化简(n+1)(n+2)(n+3) n*【n+1】*【n+2】化简成什么? n(n+1)(n+2)等于多少? n+(n-1)÷2×n 求化简 n(n+1)(n+2)什么意思 1^n+2^n+...+2013^n 当n为正偶数,求证n/(n-1)+n(n-2)/(n-1)(n-3)+...+n(n-2).2/(n-1)(n-3)...1=n 1*N+2*（N-1）+3*（N-2）+...+N*1=1/6N(N+1)(N+2) 2n*1/2^n=n/2^(n-1)?