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总题量:323 选择本页全部试题
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    在①\(a_{1}\),\(a_{3}\)的等差中项是\(3\),②\(a_{2}\),\(a_{4}\)的等比中项是\(a_{1}^{2}\),③\(a_{1}+a_{3}+a_{5}=14.\)
    这三个条件中任选择两个,补充在下面问题中并解答.如果选多种方案解答,按第一种方案计分.
    已知正项等比数列\(\{a_{n}\}\)满足 _____,____.
    \((1)\)求数列\(\{a_{n}\}\)的通项公式;
    \((2)\)记数列\(\{a_{n}\}\)的前\(n\)项积为\(T_{n}\),求数列\(\{\dfrac{1}{\log_{2}T_{n}}\}\)的前\(n\)项和\(S_{n}.\)
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    已知公差不为\(0\)的等差数列\(\{a_{n}\}\)的前\(n\)项和为\(S_{n}\),且\(S_{3}=9\),\(a_{1}\),\(a_{2}\),\(a_{5}\)成等比数列.
    \((1)\)求数列\(\{a_{n}\}\)的通项公式;
    \((2)\)若数列\(\{b_{n}\}\)满足\(b_{n}=2^{a_{n}+1}\),求数列\(\{b_{n}-a_{n}\}\)的前\(n\)项和\(T_{n}.\)
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    已知数列\(\{a_{n}\}\)是正项等比数列,满足\(a_{3}\)是\(2a_{1}\),\(3a_{2}\)的等差中项,\(a_{4}=16.\)
    \((1)\)求数列\(\{a_{n}\}\)的通项公式;
    \((2)\)若\(b_{n}=(-1)^{n}\log_{2}a_{2n+1}\),求数列\(\{b_{n}\}\)的前\(n\)项和\(T_{n}.\)
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    设\(\{a_{n}\}\)是等差数列,\(\{b_{n}\}\)是等比数列,公比大子\(0\),且\(a_{1}=b_{1}=3\),\(b_{2}=a_{3}\),\(b_{3}=4a_{2}+3.\)
    \((Ⅰ)\)求\(\{a_{n}\}\)和\(\{b_{n}\}\)的通项公式;
    \((Ⅱ)\)设数列\(\{c_{n}\}\)满足\(c_{n}=\begin{cases}{1,n\text{为奇数}}\\ {b_{\frac{n}{2}},n\text{为偶数}}\end{cases}\),求\(\sum\limits_{i=1}^{2n}a_{i}c_{i}.\)
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    已知公差不为\(0\)的等差数列\(\{a_{n}\}\)满足\(a_{3}=5\),且\(a_{1}\),\(a_{2}\),\(a_{5}\)成等比数列.
    \((Ⅰ)\)求\(\{a_{n}\}\)的通项公式;
    \((Ⅱ)\)设\(b_{n}=\dfrac{1}{3^{n}}-\dfrac{1}{a_{n}a_{n+1}}\),求数列\(\{b_{n}\}\)的前\(n\)项和\(T_{n}.\)
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    已知\(\{a_{n}\}\)为等差数列,\(\{b_{n}\}\)为等比数列,且满足\(a_{1}=1\),\(b_{1}=2\),\(a_{4}=4(a_{3}-a_{2})\),\(b_{4}=4(b_{3}-b_{2}).\)
    \((1)\)求\(\{a_{n}\}\)和\(\{b_{n}\}\)的通项公式;
    \((2)\)对任意的正整数\(n\),设\(c_{n}=a_{n}b_{n}\),求数列\(\{c_{n}\}\)的前\(n\)项和\(S_{n}.\)
  • 题型:选择题 题类:模拟题 难易度:较易

    年份:2021

    已知等比数列\(\{a_{n}\}\)中,\(a_{5}a_{11}=9a_{8}\),数列\(\{b_{n}\}\)是等差数列,且\(b_{8}=a_{8}\),则\(b_{3}+b_{13}=(\quad)\)
    A.\(18\) B.\(9\) C.\(16\) D.\(81\)
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    在等差数列\(\{a_{n}\}\)中,\(a_{1}=3\),其前\(n\)项和为\(S_{n}\),各项均为正数的等比数列\(\{b_{n}\}\)中,\(b_{1}=1\),且满足\(b_{3}=S_{2}\),\(a_{1}+a_{2}+b_{1}=10.\)
    \((Ⅰ)\)求数列\(\{a_{n}\}\)与\(\{b_{n}\}\)的通项公式;
    \((Ⅱ)\)求数列\(\{\dfrac{1}{S_{n}}\}\)的前\(n\)项和\(T_{n}.\)
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    已知等比数列\(\{a_{n}\}\)的公比为\(q(q≠1)\),前\(n\)项和为\(S_{n}\),\(S_{3}=14\),且\(3a_{2}\)是\(2a_{3}\)与\(4a_{1}\)的等差中项.
    \((1)\)求\(\{a_{n}\}\)的通项公式;
    \((2)\)设\(b_{n}=\dfrac{1}{(\log_{2}a_{n+1})(\log_{2}a_{n+2})}\),\(\{b_{n}\}\)的前\(n\)项和为\(T_{n}\),证明:\(T_{n}< \dfrac {1}{2}.\)
  • 题型:解答题 题类:模拟题 难易度:较易

    年份:2021

    已知等比数列\(\{a_{n}\}\)的公比为\(q(q≠1)\),前\(n\)项和为\(S_{n}\),\(S_{3}=14\),且\(3a_{2}\)是\(2a_{3}\)与\(4a_{1}\)的等差中项.
    \((1)\)求\(\{a_{n}\}\)的通项公式;
    \((2)\)设\(b_{n}=\dfrac{1}{(\log_{2}a_{n})(\log_{2}a_{n+2})}\),\(\{b_{n}\}\)的前\(n\)项和为\(T_{n}\),证明:\(\dfrac{1}{3}\leqslant T_{n}< \dfrac {3}{4}.\)