Sn=2^2-4^2+6^2-8^2+.+(-1)^n+1 *(2n)^2=

2Sn+Sn-1=3-8/2^n,求Sn 设Sn=2+4+6+.+2n,则1/s1+1/s2+.+1/sn= a1=1.sn=2an+1.求sn a1=1,Sn=2an+1求Sn Sn=3+2^n Sn-1=3+2^(n-1).则Sn-Sn-1=? 求和Sn=1-2 3-4+ 求和Sn=1/2+2/4+3/8+…+n/2^n,不明白Sn-1/2Sn是怎样减得不明白Sn-1/2Sn是怎样减得,Sn-1/2Sn=1/2+1/4+1/8+....+1/2^n- n/2^(n+1) 怎么来的？ 设Sn=1/2+1/6+1/12+…+1/n（n+1）,且Sn*Sn+1=3/4,则n=多少? Sn=1+2+4+...+2的N次方,求Sn sn=1+2+4+...+2^（n-1）,求sn an是等差数列,求​lim (Sn+Sn+1)/(Sn+Sn-1)lim (Sn+Sn+1)/(Sn+Sn-1)=[n(n+1)/2+(n+1)(n+2)/2]/[n(n+1)/2+n(n-1)/2]=(2n²+4n+2)/2n²=1+2/n+1/n²我就想知道第一步怎么来的 已知数列an,Sn>1,6Sn=(an +1)(an +2) 求通项 设Sn=1*4+2*7+.n(3n+1)则Sn= Sn求和 Sn=1+2x3+3x9+4x27+...+nx3的n-1次方 高二数学数列求和问题!在数列an中,a1=1,Sn为an前n项和,an=S(n-1) 求Sn,an请帮我看看我分别先算Sn和an哪里出错了?1.先算Sn因为an=2Sn-1 且an=Sn-Sn-1所以 Sn-Sn-1=2Sn-1Sn=3Sn-1所以Sn是一个等比数列 公比为3 运 已知数列{an}的中,a1=8且2an+1+an=6,其前n项和为Sn,则不等式|Sn-2n-4| 已知数列{an}中,a1=8,且2an+1 + a6=6,其前n项和为Sn,则满足不等式|Sn-2n-4| 已知数列{an}的中,a1=8且2an+1+an=6,其前n项和为Sn,则不等式|Sn-2n-4|