(-1)^n+(-1)^n-3 * (-1)^4
证明不等式:(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n
1除以(n+3)(n+4)+1除以(n+4)(n+5)+、、、1除以(n+10)(n+11)=?
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
一道数列求和题1/2n+3/4n+5/8n+...+(2n-1)/n*2^n
证明:1+2C(n,1)+4C(n,2)+...+2^nC(n,n)=3^n .(n∈N+)
81^(n+1)÷27^n÷9^(n-1)×3^(n-4)
(n-1)(n-2)(n-3)(n-4)……(n-m+1)(n-m)n大于m 的计算公式
[3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简
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/
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
(3a^n-2)-6a^n+14a^n-1(因式分解) (m-n)^3+4(n-m)