摘要:2.求下列等比数列的各项和: (1)1.3.9.-.2187, (2)1....-..
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设无穷数列{an}的前n项和为Sn,且(3-p)Sn+2pan=3+p(n∈N*),p为常数,p<-3.
(1)求证:{an}是等比数列,写出{an}的通项公式;
(2)若数列{an}的公比q=f(p),无穷数列{bn}满足:b1=a1,bn=
f(bn-1),(n≥2),求证:{
}是等差数列,并写出{bn}的通项公式;
(3)设cn=
,在(2)的条件下,有
(bnlgan)=lg27,求数列{cn}的各项和.
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(1)求证:{an}是等比数列,写出{an}的通项公式;
(2)若数列{an}的公比q=f(p),无穷数列{bn}满足:b1=a1,bn=
| 3 |
| 2 |
| 1 |
| bn |
(3)设cn=
| 1 |
| an-an+1 |
| lim |
| n→∞ |