(1+2+3+...+2n)/(1+3+5+...+(2n-1))=21/10求n的值
若n²+3n=1,求n(n+1)(n+2)+1的值.
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
若3n^2-n=1,求6n^3+7n^2-5n+2003的值
证明不等式:(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n
证明(1+2/n)^n>5-2/n(n属于N+,n>=3)
化简:当n=1/2时,求(3n-1)(n+1)+(2n-1)(n-1)的值.
已知an=5n(n+1)(n+2)(n+3),求数列{an}的前n项和Sn
求(1^n+2^n+3^n)^1/n,n趋于无穷大的极限
求极限Xn=n/(n^2+1)+n/(n^2+2)+n/(n^2+3)+……+n/(n^2+n),
若(3m-2n+1)与|5m=2n-n|互为相反数,求m+n的值
lim((n^2+2n-1)/(2n^2-n+3))的值 求详解
求数列an=n(n+1) 的前n项和 到 an=n(n+1)=[n(n+1)(n+2)-(n-1)n(n+1)]/3(裂