3*2^(n+1)=360 求n

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 求极限Xn=n/(n^2+1)+n/(n^2+2)+n/(n^2+3)+……+n/(n^2+n), 数列a(n)=n (n+1)(n+2)(n+3), 求S(n)怎么用高中数列原理解答? 已知1/n^2+3n=A/n+B/n+3,求ab? 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 化简：当n=1/2时,求(3n-1)(n+1)+(2n-1)(n-1)的值. 若3n^2-n=1,求6n^3+7n^2-5n+2003的值 f(n)=1/(n+1) + 1/(n+2) + 1/(n+3) + …… + 1/(2n),(n∈整数,且n≥2),求 已知an=5n(n+1)(n+2)(n+3),求数列{an}的前n项和Sn 已知Sn=2+5n+8n^2+…+(3n-1)n^n-1(n∈N*)求Sn 证明不等式：(1/n)^n+(2/n)^n+(3/n)^n+.+(n/n)^n