设等差数列{an}的前n项和为Sn,等比数列{bn}的前n项和为Tn,已知bn>0(n∈N*),a1=b1=1,a2+b3=a3,S5=5(T3+b2).(Ⅰ)求数列{an},{bn}的通项公式;(Ⅱ)求和:b1T1T2+b2T2T3+…+bnTnTn+1.

问题描述:

设等差数列{an}的前n项和为Sn,等比数列{bn}的前n项和为Tn,已知bn>0(n∈N*),a1=b1=1,a2+b3=a3,S5=5(T3+b2).
(Ⅰ)求数列{an},{bn}的通项公式;
(Ⅱ)求和:

b1
T1T2
+
b2
T2T3
+…+
bn
TnTn+1

(Ⅰ)设{an}的公差为d,数列{bn}的公比为q,则∵a1=b1=1,a2+b3=a3,S5=5(T3+b2),∴q2=d,1+2d=1+2q+q2,∴q2-2q=0,∵q≠0,∴q=2,∴d=4∴an=4n-3,bn=2n-1;(Ⅱ)∵bnTnTn+1=bn+1qTnTn+1=1q(1Tn−1Tn+1)∴...
答案解析:(Ⅰ)利用等差数列、等比数列的通项与求和公式,求出公差与公比,即可求得结论;
(Ⅱ)利用裂项法,即可求数列的和.
考试点:等差数列与等比数列的综合;数列的求和.


知识点:本题考查了等差与等比数列的综合计算,考查裂项法的运用,属于中档题.