{an}为等差数列,其前n项和为Sn,a3=1/2.S3=6.求1/S1+1/S2+1/S3+...+1/Sn
问题描述:
{an}为等差数列,其前n项和为Sn,a3=1/2.S3=6.
求1/S1+1/S2+1/S3+...+1/Sn
答
{an}为等差数列,其前n项和为Sn,a3=1/2.S3=6.
求1/S1+1/S2+1/S3+...+1/Sn