1/1×4+1/4×7...1/(3n-2)×(3n+1) 1/1×3+1/3×5...1/（2n-1）×（2n+1）

证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n 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 [3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简 化简(n+1)(n+2)(n+3) 一道数列求和题1/2n+3/4n+5/8n+...+（2n-1）/n*2^n 证明：1+2C(n,1)+4C(n,2)+...+2^nC(n,n)=3^n .(n∈N+) 计算：n(n+1)(n+2)(n+3)+1 lim[(n+3)/(n+1))]^(n-2) 【n无穷大】 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^2 n 1 ) 2/(n^2 n 2) 3/(n^2 n 3) ……n/(n^2 n n)) 当N越于无穷大 1 + (n + 1) + n*(n + 1) + n*n + (n + 1) + 1 = 2n^2 + 3n + 3