(1/1+2)+(1/2+3)+(1/3+4)+.+(1/n+(n+1))等于?
证明不等式:(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n
n(n+1)(n+2)等于多少?
Sn=n(n+2)(n+4)的分项等于1/6[n(n+2)(n+4)(n+5)-(n-1)n(n+2)(n+4)]吗?
+(n-1)!+(n-2)!+.+(n-n)!等于什么?
一道数学题、1+2+3+4+---------+n=n/2(1+n)为什么等于n/2(1+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
∵ n(n+1)(n+2)(n+3)+1 等于?
∑(N等于1,2,3,4..n) 5^N/N!,极限怎么求
化简(n+1)(n+2)(n+3)
1+2+3+4+……+(n-1)为什么等于n(n-1)/2