1 |
S1 |
1 |
S2 |
1 |
S3 |
1 |
Sn |
3 |
4 |
(a1+a7) |
2 |
8(4n-1) |
3 |
n(n+1) |
2 |
n(n-1) |
2 |
1 |
Sn |
1 |
n(n+2) |
1 |
2 |
1 |
n |
1 |
n+2 |
1 |
S1 |
1 |
S2 |
1 |
Sn |
1 |
2 |
1 |
3 |
1 |
2 |
1 |
4 |
1 |
n |
1 |
n+2 |
1 |
2 |
1 |
2 |
1 |
1+n |
1 |
n+2 |
3 |
4 |
2n+3 |
2(n+1)(n+2) |
3 |
4 |
A.40 | B.35 | C.30 | D.25 |
A.S1,S2…S8都小于0,S9,S10…都大于0 |
B.S1,S2…S16都小于0,S17,S18…都大于0 |
C.S1,S2,S3,S4都小于0,S5,S6…都大于0 |
D.S1,S2…S15都小于0,S16,S17…都大于0 |
A.44 | B.22 | C.
| D.88 |
A.18 | B.99 | C.198 | D.297 |
A.20 | B.25 | C.30 | D.35 |
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