3×9^n×27^n-1
计算9^n*(1/27)^n+1*3^n+2
9^n+1--3^n=27,求n
3×9^n×27^n-1
81^(n+1)÷27^n÷9^(n-1)×3^(n-4)
证明不等式:(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n
1\n(n+3)+1\(n+3)(n+6)+1\(n+6)(n+9)=1\2 n+18 n为正整数,求n的值
lim 9^n+4^n+2/5^n-3^2n-1 n趋于无穷大时
lim(3^2n+5^n)/(1+9^n)
3×9的n次方×27的n-1次方
:9^n×27^n-1÷3^3n+1=81,求n^-2 的值.
[3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简
化简(n+1)(n+2)(n+3)