高二数学数列试卷
问题描述：
高二数学数列试卷
Sn=1*（1/2）+3*（1/4）+5*（1/8）+...+(2n-1/2的n次方)
求和
答
Sn= 1*(1/2)+3*(1/4)+5*(1/8)+……+(2n-1)*(1/2^n)2Sn=1*1+3*(1/2)+5*(1/4)+……+(2n-1)*[1/2^(n-1)]2Sn-Sn=1+[2*(1/2)+2*(1/4)+……+2*(1/2^(n-1))]-(2n-1)*(1/2^n)所以Sn=1+[1-1/2^(n-2)]-(2n-1)*(1/2^n)=2-1/2^(n...