1-(1/(2n+1))怎样化简成n/(n+1)

2^n/n*(n+1) 证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n 怎样证明n/(n+1) [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 (n+1)^n-(n-1)^n=? 化简(n+1)(n+2)(n+3) n(n+1)(n+2)数列求和 n(n+1)(n+2)等于多少? 9n^2+3n-2怎样化简为(3n-1)(3n+2) 化简[n^2+(n+1)^2]/n(n+1) 化简额 计算：n(n+1)(n+2)(n+3)+1 阶乘(2n-1)!=（2n)!/(2^n*n!