题目内容
若两等差数列{an}、{bn}前n项和分别为An、Bn,满足
=
(n∈N+),则
的值为( )
An |
Bn |
7n+1 |
4n+27 |
a11 |
b11 |
A.
| B.
| C.
| D.
|
∵数列{an}、{bn}是等差数列,且其前n项和分别为An、Bn,
由等差数列的性质得,A21=
=21a11,B21=
=21b11,
∵足
=
(n∈N+),
∴
=
=
=
=
.
故选:C.
由等差数列的性质得,A21=
(a1+a21)×21 |
2 |
(b1+b21)×21 |
2 |
∵足
An |
Bn |
7n+1 |
4n+27 |
∴
a11 |
b11 |
21a11 |
21b11 |
A21 |
B21 |
7×21+1 |
4×21+27 |
4 |
3 |
故选:C.
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