解(n-2)/n:(2n-2)/2n=3:4如题,解出来

n+(n+1)+(n+2)+(n+3)+(n+4)=5n+10这道题怎么解 证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^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 高数题：n趋近于0,lim｛1/（n^2+n+1)+2/(n^2+n+2)+3/(n^2+n+3)+.+n/(n^2+n+n)｝=? 为什么n(n+1)(n+2)(n+3)=(n²+3n+2)(n²+3n)? 为什么:n×(n+1)=1/3[n(n+1)×(n+2)-(n-1)×n×(n+1)] 数列a(n)=n (n+1)(n+2)(n+3),求S(n) n(n-1)(n-2)（n-3)（n-4)=154440.求N值 要步骤 2^n/n*(n+1) 解方程：2n（n-3)/2=n (n-2):(2n-n)=3:16怎么解 n(n-3)/2=3n怎么解? [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+3=n+2怎么解