问题
填空题
已知两个等差数列{an}和{bn}的前n和分别为An和Bn,且
|
答案
∵两个等差数列{an}和{bn}的前n和分别为An和Bn,
且
An |
Bn |
2n+1 |
n+3 |
∴
a9 |
b9 |
2a9 |
2b9 |
a1+a17 |
b1+b17 |
=
| ||
|
A17 |
B17 |
=
2×17+1 |
17+3 |
7 |
4 |
故答案为:
7 |
4 |
已知两个等差数列{an}和{bn}的前n和分别为An和Bn,且
|
∵两个等差数列{an}和{bn}的前n和分别为An和Bn,
且
An |
Bn |
2n+1 |
n+3 |
∴
a9 |
b9 |
2a9 |
2b9 |
a1+a17 |
b1+b17 |
=
| ||
|
A17 |
B17 |
=
2×17+1 |
17+3 |
7 |
4 |
故答案为:
7 |
4 |