Let {an} be an arithmetic sequence, Sn be the sum of its first n terms, and s5s8, ask: is A7 = 0 right?

Of course, it is equal to 0! Because S6 = S7 and S7 = a1 + A2 + a3 + A4 + A5 + A6, S7 = a1 + A2 + a3 + A4 + A5 + A6 + A7. So A7 = s7-s6 = 0, as for S50, S7 > S8 can get A8

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