已知数列{an}的前n项和Sn=2n2(n∈N*),等比数列{bn}满足:a1=b1,b2(a3-a2)=b1(an-an-2)(n≥3). (1)求{an}及{bn}的通项公式; (2)设cn=anbn,求数列{cn}的前n项和Tn.
问题描述:
已知数列{an}的前n项和Sn=2n2(n∈N*),等比数列{bn}满足:a1=b1,b2(a3-a2)=b1(an-an-2)(n≥3).
(1)求{an}及{bn}的通项公式;
(2)设cn=
,求数列{cn}的前n项和Tn. an bn
答
(1)∵Sn=2n2(n∈N*),∴n=1时,a1=S1=2;n≥2时,an=Sn-Sn-1=4n-2,a1=2也满足上式∴an=4n-2∵数列{bn}是等比数列,且a1=b1,b2(a3-a2)=b1(an-an-2)(n≥3).∴数列{bn}的公比q=b2b1=an−an−2a3−a2=2...