作业帮n(n+1)/2+1/3n（n+1）(n-1)=一步一步,
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n(n+1)/2+1/3n（n+1）(n-1)=一步一步,
n(n+1)/2+1/3n（n+1）(n-1)=
一步一步,
n(n+1)/2+1/3n（n+1）(n-1)=一步一步,
n(n+1)/2+1/3n（n+1）(n-1)
=(n^2+n)/2+n(n^2-1)/3
=1/2*n^2+1/2n+1/3*n^3-1/3*n
=1/3*n^3+1/2*n^2+1/6*n
证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n
2^n/n*(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)
2n/（n+1）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
1*N+2*（N-1）+3*（N-2）+...+N*1=1/6N(N+1)(N+2)
(n+2)!/(n+1)!
判断 当n>1时,n*n*n>3n.( )
lim2^n +3^n/2^n+1+3^n+1
n(n+1)(n+2)(n+3)+1 因式分解
n(n+1)(n+2)(n+3)+1等于多少
3(n-1)(n+3)-2(n-5)(n-2)
lim(n+3)(4-n)/(n-1)(3-2n)
lim(n^3+n)/(n^4-3n^2+1)