求和4^n+3×4^(n-1)+3^2×4(n-2)+……+3^(n-1)×4+3^n

求和4^n+3×4^(n-1)+3^2×4(n-2)+……+3^(n-1)×4+3^n 一道数列求和题1/2n+3/4n+5/8n+...+（2n-1）/n*2^n 求和sn＝1×2×3+2×3×4+……+n(n+1)(n+2) 1*2*3+2*3*4+……+n(n+1)(n+2) 求和 求和：Sn=1*2*3+2*3*4+……+n(n+1)(n+2) 1/2!+2/3!+3/4!+.+n/(n+1)!求和 求和(1+2)+(3+4)+...+(2n-1+2^n) 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 lim(1/n^2+4/n^2+7/n^2+…+3n-1/n^2) 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 求和：1+(2n+3)+(4n+5)+.+2n^2-1=