职教组卷基于海量职教高考试题库建立的在线组卷及学习系统
职教组卷
  • 题型:填空题 题类:期末考试 难易度:中档

    已知数列\(\{a _{n} \}\)和\(\{b _{n} \}\),满足\(b _{n} =1- \dfrac {2}{a_{n}}\),设\(\{b _{n} \}\)的前\(n\)项积为\( \dfrac {2}{a_{n}}\),则\(\{ \dfrac {4}{a_{n}a_{n+1}} \}\)的前\(n\)项的和\(S _{n} =\)______.
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