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
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  • 题型:解答题 题类:历年真题 难易度:较难

    年份:2018

    已知等差数列\(\{a_{n}\}\)的公差不为零,\(a_{1}=25\),且\(a_{1}\),\(a_{11}\),\(a_{13}\)成等比数列.
    \((\)Ⅰ\()\)求\(\{a_{n}\}\)的通项公式;
    \((\)Ⅱ\()\)求\(a_{1}+a_{4}+a_{7}+…+a_{3n-2}\).
  • 题型:解答题 题类:历年真题 难易度:较难

    年份:2018

    已知数列\(\{a_{n}\}\)的前\(n\)项和为\(S_{n}\),且\(S_{n}=2a_{n}-2\).
    \((1)\)求数列\(\{a_{n}\}\)的通项公式;
    \((2)\)若数列\(\{ \dfrac {n+1}{a_{n}}\}\)的前\(n\)项和为\(T_{n}\),求\(T_{n}\).
  • 题型:解答题 题类:历年真题 难易度:较难

    年份:2018

    已知等差数列\(\{a_{n}\}\)的公差\(d\)不为零,\(a_{4}^{2}=-a_{1}a_{6}\),且\(a_{2}\neq 0\).
    \((1)\)求\(a_{1}\)与\(d\)的关系式;
    \((2)\)当\(d= \dfrac {2}{9}\)时,设\(b_{n}= \dfrac {2}{81a_{n}a_{n+1}}\),求数列\(\{b_{n}\}\)的前\(n\)项和\(S_{n}\).
  • 题型:解答题 题类:历年真题 难易度:较难

    年份:2018

    设数列\(\{a_{n}\}\)满足\(a_{1}=1,a_{n+1}=a_{n}+n+1(n∈N^{*})\).
    \((1)\)求数列\(\{a_{n}\}\)的通项公式;
    \((2)\)若数列\(\{ \dfrac {1}{a_{n}}\}\)的前\(n\)项和为\(T_{n}\),求\(T_{n}\).