S
∵ Sn Tn= 7n+3 n+3 ∴ a8 b8= 2a8 2b8= a1+a15 b1+b15=
15 2(a1+a15)
15 2(b1+b15) = S15 T15= 7×15+3 15+3=6 故答案为:6
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