1 |
S1 |
1 |
S2 |
1 |
Sn |
3 |
4 |
3 |
2 |
2 |
3 |
2 |
3 |
n(n-1)d |
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 |
3 |
1 |
5 |
1 |
n-1 |
1 |
n+1 |
1 |
n |
1 |
n+2 |
1 |
2 |
1 |
2 |
1 |
n+1 |
1 |
n+2 |
3 |
4 |
1 |
2(n+1) |
1 |
2(n+2) |
3 |
4 |
c1 |
b1 |
c2 |
b2 |
cn |
bn |
A.x1,x2,x3成等差数列 | B.x1,x3,x2成等差数列 |
C.y1,y2,y3成等差数列 | D.y1,y3,y2成等差数列 |
1 |
4an2-1 |
3 |
anan+1 |
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