1/n+1 + 1/n+2 + 1/n+3 +.+1/2n>a对于一切大于1的自然数n都成立,求a的范围

2^n/n*(n+1) 证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n (n+2)!/(n+1)! n^(n+1/n)/(n+1/n)^n [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 (n+1)^n-(n-1)^n=? 化简：(n+1)!/n!-n!/(n-1)! (n-1)*n!+(n-1)!*n 推导 n*n!=(n+1)!-n! 化简(n+1)(n+2)(n+3) n*【n+1】*【n+2】化简成什么? 2n/（n+1）n! n(n+1)(n+2)等于多少? n+(n-1)÷2×n 求化简