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总题量:365 选择本页全部试题
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    设\(\{a_{n}\}\)是公比为负数的等比数列,\(3a_{1}\)为\(a_{2}\),\(a_{3}\)的等差中项,\(a_{5}=-243.\)
    \((Ⅰ)\)求数列\(\{a_{n}\}\)的通项公式;
    \((Ⅱ)\)设\(b_{n}=a_{2n}+a_{2n-1}\),求数列\(\{b_{n}\}\)的前\(n\)项和\(T_{n}.\)
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    设数列\(\{a_{n}\}\)前\(n\)项和为\(S_{n}\),\(a_{1}=1\),\(a_{n+1}-S_{n}=1(n\in N*).\)
    \((Ⅰ)\)求出\(\{a_{n}\}\)通项公式;
    \((Ⅱ)\)若\(b_{n}=\begin{cases}\dfrac{1}{n(n+2)},n\text{为奇数}\\ \dfrac {n}{a_{n+1}},n\text{为偶数}\end{cases}\),求数列\(\{b_{n}\}\)的前\(2n\)项和\(T_{2n}.\)
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    已知公差不为\(0\)的等差数列\(\{a_{n}\}\),满足\(a_{4}^{2}=a_{2}a_{9}\),\(a_{3}+a_{5}+a_{7}=39\),记\(b_{n}=[\log_{5}a_{n}]\),其中\([x]\)表示不超过\(x\)的最大整数,如\([0.8]=0\),\([\log_{5}26]=2.\)
    \((1)\)求\(\{a_{n}\}\)的通项公式;
    \((2)\)求数列\(\{b_{n}\}\)的前\(2022\)项和.
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    在公差不为\(0\)的等差数列\(\{a_{n}\}\)中,前\(n\)项和为\(S_{n}\),\(S_{4}=2(a_{4}+1)\),\(a_{2}^{2}+a_{6}^{2}=a_{4}^{2}+a_{5}^{2}.\)
    \((1)\)求数列\(\{a_{n}\}\)的通项公式;
    \((2)\)若\(b_{n}=\dfrac{1}{a_{n}\cdot a_{n+1}}\),求数列\(\{b_{n}\}\)的前\(n\)项和为\(T_{n}.\)
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    已知数列\(\{a_{n}\}\)的各项均为正数,其前\(n\)项和\(S_{n}\)满足\(4S_{n}=(a_{n}+1)^{2}.\)
    \((1)\)证明:数列\(\{a_{n}\}\)是等差数列;
    \((2)\)设数列\(b_{n}=\dfrac{1}{a_{n}\cdot a_{n+1}}\),求数列\(\{b_{n}\}\)的前\(n\)项和\(T_{n}.\)
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    已知数列\(\{a_{n}\}\)的各项均为正数,\(S_{n}\)表示数列\(\{a_{n}\}\)的前\(n\)项的和,且\(S_{n}=n^{2}+2n.\)
    \((1)\)求数列\(\{a_{n}\}\)的通项公式;
    \((2)\)设\(b_{n}=\dfrac{2}{a_{n}a_{n+1}}\),求数列\(\{b_{n}\}\)的前项\(n\)和\(T_{n}.\)
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    已知数列\(\{a_{n}\}\),\(a_{1}=\dfrac{1}{2}\),\(2a_{n+1}=a_{n}+1.\)
    \((1)\)证明\(\{a_{n}-1\}\)是等比数列;
    \((2)\)求数列\(\{a_{n}\}\)的前\(n\)项和\(S_{n}.\)
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    等比数列\(\{a_{n}\}\)中,首项\(a_{1}=\dfrac{1}{3}\),公比\(q>0\),\(q≠1\),且\(a_{1}\),\(5a_{3}\),\(9a_{5}\)成等差数列.
    \((Ⅰ)\)求\(\{a_{n}\}\)的通项公式;
    \((Ⅱ)\)令\(b_{n}=\log_{3}\dfrac{1}{a_{n}}\),求数列\(\{\dfrac{1}{b_{n}b_{n+1}}\}\)的前\(n\)项和为\(T_{n}.\)
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    已知数列\(\{a_{n}\}\),\(\{b_{n}\}\),\(S_{n}\)为数列\(\{a_{n}\}\)的前\(n\)项和,\(a_{2}=4b_{1}\),\(S_{n}=2a_{n}-2\),\(nb_{n+1}-(n+1)b_{n}=n^{2}+n(n\in N^{*})\)
    \((Ⅰ)\)求数列\(\{a_{n}\}\)的通项公式;
    \((Ⅱ)\)证明\(\{\dfrac{b_{n}}{n}\}\)为等差数列;
    \((Ⅲ)\)若数列\(\{c_{n}\}\)的通项公式为\(c_{n}=\begin{cases}-\dfrac{a_{n}b_{n}}{2},n\text{为奇数}\\ \dfrac {a_{n}b_{n}}{4},n\text{为偶数}\end{cases}\),令\(T_{n}\)为\(\{c_{n}\}\)的前\(n\)项的和,求\(T_{2n}.\)
  • 题型:解答题 题类:期中考试 难易度:较易

    年份:2021

    已知数列\(\{a_{n}\}\)是等差数列,设\(S_{n}(n\in N*)\)为数列\(\{a_{n}\}\)的前\(n\)项和,数列\(\{b_{n}\}\)是等比数列,\(b_{n}>0\),若\(a_{1}=3\),\(b_{1}=1\),\(b_{3}+S_{2}=12\),\(a_{5}-2b_{2}=a_{3}.\)
    \((Ⅰ)\)求数列\(\{a_{n}\}\)和\(\{b_{n}\}\)的通项公式;
    \((Ⅱ)\)求数列\(\{a_{n}\boldsymbol{⋅}b_{n}\}\)的前\(n\)项和.