n(a1+an) |
2 |
k(a1+ak) |
2 |
(k+1)(a1+ak+1) |
2 |
(a1+ak+1) |
2 |
k(a1+ak) |
2 |
(n-1)(a1+an-1) |
2 |
n(a1+an) |
2 |
n(a1+an) |
2 |
(n-1)(a1+an-1) |
2 |
(n+1)(a1+an-1) |
2 |
n(a1+an) |
2 |
(n+1)(a1+an-1) |
2 |
(n-1)(a1+an-1) |
2 |
A.S4<S5 | B.S4=S5 | C.S6<S5 | D.S6=S5 |
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