已知数列{an}的前n项和为Sn,且满足a1=1,an+SnSn-1=0 an=1/n(1-n), Sn=1/n求证:S1^2+ S2^2+S3^2+……Sn^2 ≤2-1/n因Sn=1/n,所以S1^2+ S2^2+S3^2+……Sn^2==1+1/2^2+1/3^2+……+1/n^2因为1/2^2...