1.已知等差数列{an}与{bn}的前n项之和分别是Sn与Tn,若Sn/Tn=(2n+2)/(n+3),求a7/b7的值.
问题描述:
1.已知等差数列{an}与{bn}的前n项之和分别是Sn与Tn,若Sn/Tn=(2n+2)/(n+3),求a7/b7的值.
2.设等差数列{an}的前n项之和为Sn,若a3=12,S12>0,S130,n>=2,n属于正整数).
(1)求证{an}是等比数列,并求公比f(t);
(2)设数列{bn}满足b1=1,bn=f(1/bn-1) n>=2,n属于正整数.求和b1b2-b2b3+b3b4-…+b2n-1b2n-b2nb2n+1.
4.已知数列{an}成等比数列,且an>0,若bn=log3(an),且b1+b2+b3=-3,b1b2b3=3,求an的表达式.
答
还差一问