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问题: 数列{an}中,a1=1,当n>=2时,前n项和Sn满足Sn^2=an(Sn-1/2).求Sn

解答:

Sn^2=an(Sn-1/2)=[Sn -S(n-1)](Sn -1/2)
==> S(n-1) =Sn +2*Sn*S(n-1) ==> 1/Sn =1/S(n-1) +2
{Sn}为等差数列,公差=2,首项1/S1 =1/a1 =1 ==> 1/Sn =2n-1
==> Sn =1/(2n-1)