设数列{an}中,Sn是其前n项和,若首项a1=1,且满足2Sn^2=an(2Sn-1),(n为下标),(n∈N*,n≥2),求通项.
问题描述:
设数列{an}中,Sn是其前n项和,若首项a1=1,且满足2Sn^2=an(2Sn-1),(n为下标),(n∈N*,n≥2),求通项.
不要跳步,
答
利用an=Sn-S(n-1)即2Sn^2=(Sn-S(n-1))(2Sn - 1)2Sn^2=2Sn^2-2SnS(n-1) -Sn+S(n-1)2SnS(n-1)+Sn-S(n-1)=0Sn=S(n-1)/(2S(n-1)+1)取倒数1/Sn=2+1/S(n-1)所以1/Sn是以1/S1=1/a1=1为首项公差为2的等差数列所以1/Sn=1+2(n-...