化简:1/2!+2/3!+3/4!+4/5!+.+(n-1)/n!
化简:1/(n+1)(n+2)+1/(n+2)(n+3)+1/(n+3)(n+4)
lim 9^n+4^n+2/5^n-3^2n-1 n趋于无穷大时
(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
证明不等式:(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n
一道数列求和题1/2n+3/4n+5/8n+...+(2n-1)/n*2^n
化简(n+1)(n+2)(n+3)
已知888个连续正整数之和:n+(n+1)+(n+2)+(n+3)+(n+4)+(n+5)+(n+6)+(n+7)+··
证明:1+2C(n,1)+4C(n,2)+...+2^nC(n,n)=3^n .(n∈N+)
用数学归纳法证明:1×2×3+2×3×4+…+n×(n+1)×(n+2)=n(n+1)(n+2)(n+3)4(n∈N
若n为正整数,求1/n(n+1)+1/(n+1)(n+2)+1/(n+2)(n+3)+1/(n+3)(n+4)+.+1/
lim(1/n^2+4/n^2+7/n^2+…+3n-1/n^2)