1 |
2 |
a9+a10 |
a7+a8 |
A.1+
| B.1-
| C.3+2
| D.3-2
|
1 |
2 |
2 |
2 |
a9+a10 |
a7+a8 |
a1q8 +a1q9 |
a1q6+a1q7 |
2 |
A.以7为首项,公差为2的等差数列 |
B.以7为首项,公差为5的等差数列 |
C.以5为首项,公差为2的等差数列 |
D.不是等差数列 |
1 |
4 |
A.30 | B.45 | C.50 | D.80 |
A.2 | B.3 | C.-2 | D.-3 |
A.8 | B.9 | C.17 | D.18 |
A.0° | B.15° | C.30° | D.45° |
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