求使1+2+3+4+5+…+n
线性代数求n阶行列式row1:1 2 3 4 … n-2 n-1 n.row2:2 3 4 5 … n-1 n 1.ro
求极限lim(1/2n+3/4n+……+(2^n-1)/(2^n*n))
已知Sn=2+5n+8n^2+…+(3n-1)n^n-1(n∈N*)求Sn
求数列Cn=2^n(2n-1)的前n项和Tn=2*1+4*3+8*5+…+2^n(2n-1)
求极限 lim(n->无穷)[(3n^2-2)/(3n^2+4)]^[n(n+1)]
求lim(n+1)(n+2)(n+3)/(n^4+n^2+1)
求数列1*2*3,2*3*4,4*5*6,…n(n+1)(n+2),…的Sn
求极限Xn=n/(n^2+1)+n/(n^2+2)+n/(n^2+3)+……+n/(n^2+n),
求数列的前n项和1/2,3/4,5/8,…,2n-1/2^n,…
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/
1+4-7+10-……+(-1)^n(3n+2) 求前N项和
求[(1*2*4+2*4*8+…+n*2n*4n)/(1*3*9+2*6*18+...+n*3n*9n)]^2