已知数列{an}是等差数列,数列{bn}是等比数列,又a1=b1=1,a2b2=2,a3b3=7/4(1)求数列{an}及数列{bn}(2)设cn=anbn,求数列{cn}的前n项和Sn

问题描述:

已知数列{an}是等差数列,数列{bn}是等比数列,又a1=b1=1,a2b2=2,a3b3=7/4
(1)求数列{an}及数列{bn}
(2)设cn=anbn,求数列{cn}的前n项和Sn