化简：2n/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 化简(n+1)(n+2)(n+3) 2^n/n*(n+1) 化简[n^2+(n+1)^2]/n(n+1) 化简额 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+2)!/(n+1)! 根号【（2n+1）/（n²+n）】平方-4/（n平方+n ）化简 f(x)=e^x-x 求证(1/n)^n+(2/n)^n+...+(n/n)^n 化简：2^4n+1-(4^2n+16^n) 化简:2^4n+1-(4^2n+16^n) [n+(n+1)+(n+2)+……+1]化简 1/3[n（n+1）（n+2）]化简 化简3n(3n+1)(3n+2) (m+n)（m-n）-（1-2n)化简