• 两等差数列{an},{bn},前n项和分别为Sn、Tn,SnTn=7n+5n+3,则a7b7= .试题及答案-填空题-云返教育

    • 试题详情

      两等差数列{an},{bn},前n项和分别为Sn、Tn
      Sn
      Tn
      =
      7n+5
      n+3
      ,则
      a7
      b7
      =         

      试题解答


      6
      解:由题意可得
      a7
      b7
      =
      13a7
      13b7
      =
      13
      a1+a13
      2
      13
      b1+b13
      2
      =
      S13
      T13
      =
      7×13+5
      13+3
      =6
      故答案为:6

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