Arithmetic sequence a1 + a3 = 4, A4 + A6 = 12, a8 + A10 =?

a1+a3=4
a4+a6=12
3d+3d=8
6d=8
d=4/3
a8+a10=a1+7d+a3+7d=a1+a3+14d=4+14d
=4+14*4/3
=68/3

In the arithmetic sequence {an}, A3 + A1 = 37, then A2 + A4 + A6 + A8=

a3+a7=37
a2+a8=a4+a6=a3+a7
a2+a4+a6+a8=2*37=74

In the arithmetic sequence {an}, A6 = A3 + A8, then S9=______ ．

Let the tolerance of {an} be D, and the first term be A1. From the meaning of the question, we can get that a1 + 5D = a1 + 2D + A1 + 7d, ｜ a1 + 4D = 0, S9 = 9a1 + 9 × 82d = 9 (a1 + 4D) = 0, so the answer is 0

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