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总题量:151 选择本页全部试题
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    设数列\(\{a _{n} \}\)满足:\(a _{1} =1\),\(3a _{n+1} -a _{n} +4=0\),\(n∈N*\).
    \((1)\)求证:数列\(\{a _{n} +2\}\)为等比数列,并求出\(\{a _{n} \}\)的通项公式;
    \((2)\)若\(b _{n} =a _{n} +\log _{3} (a _{n} +2)\),求数列\(\{b _{n} \}\)的前\(n\)项和\(S _{n}\).
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    已知数列\(\{a _{n} \}\)的前\(n\)项和为\(S _{n}\),且\(2S_{n}=n^{2}+n (n∈N ^{*} )\),数列\(\{b _{n} \}\)为等比数列,且\(b _{2} =a _{4}\),\(b _{1} +b _{3} =S _{4}\).
    \((1)\)求\(\{a _{n} \}\)和\(\{b _{n} \}\)的通项公式;
    \((2)\)若数列\(\{b _{n} \}\)为递增数列,设\(c_{n}=(-1)^{n}a_{n}\cdot b_{n}\),求数列\(\{c _{n} \}\)的前\(n\)项和\(T _{n}\).
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    已知数列\(\{a _{n} \}\)是等差数列,且满足\(a _{6} =6+a _{3}\),\(a _{6} -1\)是\(a _{5} -1\)与\(a _{8} -1\)的等比中项.
    \((1)\)求数列\(\{a _{n} \}\)的通项公式;
    \((2)\)已知数列\(\{b _{n} \}\)满足\(b _{n} =2 ^{n} \boldsymbol{⋅}a _{n}\),求数列\(\{b _{n} \}\)的前\(n\)项和\(S _{n}\).
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    已知数列\(\{a _{n} \}\),\(\{b _{n} \}\)满足\(a_{1}= \dfrac {1}{2}\),\(a _{n+1} =a _{n} (a _{n} +1)\),\(b_{n}= \dfrac {1}{a_{n}+1}\),\(\{b _{n} \}\)的前\(n\)项和为\(S _{n}\),前\(n\)项积为\(T _{n}\).
    \((1)\)证明:\(S _{n} +2T _{n}\)是定值;
    \((2)\)试比较\(S _{n}\)与\(T _{n}\)的大小.
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    已知数列\(\{a _{n} \}\)中,\(a _{1} =1\),其前\(n\)项和为\(S _{n}\),且满足\(a _{n} +2S _{n} S _{n-1} =0(n\geqslant 2)\).
    \((1)\)求证:数列\(\{ \dfrac {1}{S_{n}}\}\)是等差数列;
    \((2)\)记\(b_{n}= \dfrac {1}{2n+1}S_{n}\),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:中档

    年份:2020

    已知数列\(\{a _{n} \}\)的前\(n\)项和为\(S _{n}\),且满足\(2S_{n}+a_{n}-n=0(n∈N^{*})\).
    \((1)\)求证:数列\(\{a_{n}- \dfrac {1}{2}\}\)为等比数列;
    \((2)\)求数列\(\{a _{n} -n\}\)的前\(n\)项和\(T _{n}\).
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    已知数列\(\{a _{n} \}\),\(\{b _{n} \}\)满足\(a _{1} =b _{1} =1\),对任意\(n∈N*\)均有\(a_{n+1}=a_{n}+b_{n}+ \sqrt { a_{ n }^{ 2 }+ b_{ n }^{ 2 }}\),\(b_{n+1}=a_{n}+b_{n}- \sqrt { a_{ n }^{ 2 }+ b_{ n }^{ 2 }}\),
    \((1)\)证明:数列\(\{a _{n} +b _{n} \}\)和数列\(\{a _{n} \boldsymbol{⋅}b _{n} \}\)均为等比数列;
    \((2)\)设\(c_{n}=(n+1)\cdot 2^{n}\cdot ( \dfrac {1}{a_{n}}+ \dfrac {1}{b_{n}})\),求数列\(\{c _{n} \}\)的前\(n\)项和\(T _{n}\).
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    设\(\{a _{n} \}\)是等差数列,\(\{b _{n} \}\)是等比数列.已知\(a _{1} =1\),\(b _{1} =2\),\(b _{2} =2a _{2}\),\(b _{3} =2a _{3} +2\).
    \((1)\)求\(\{a _{n} \}\)和\(\{b _{n} \}\)的通项公式;
    \((2)\)数列\(\{c _{n} \}\)满足\(c _{n} = \begin{cases} {1,n=2^{k}} \\ {a_{n},n\neq 2^{k}}\end{cases} (k∈N)\),设数列\(\{c _{n} \}\)的前\(n\)项和为\(S _{n}\),求\(S _{2^{n}}\).
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    已知数列\(\{a _{n} \}\)是首项为\(1\)的等差数列,数列\(\{b _{n} \}\)是公比不为\(1\)的等比数列,且满足\(a _{1} +a _{2} =b _{2}\),\(a _{2} +a _{3} =b _{3}\),\(a _{4} +a _{5} =b _{4}\).
    \((1)\)求数列\(\{a _{n} \}\),\(\{b _{n} \}\)的通项公式;
    \((2)\)令\(c_{n}= \dfrac {a_{n+2}b_{n+2}}{(a_{n}b_{n}+1)(a_{n+1}b_{n+1}+1)}(n∈N^{*})\),记数列\(\{c _{n} \}\)的前\(n\)项和为\(S _{n}\),求证:对任意的\(n∈N*\),都有\(1 < S_{n} < \dfrac {4}{3}\);
    \((3)\)若数列\(\{d _{n} \}\)满足\(d _{1} =1\),\(d _{n} +d _{n+1} =b _{n}\),记\(T_{n}= \sum\limits_{k=1}^{n} \dfrac {d_{k}}{b_{2k}}\),是否存在整数\(λ\),使得对任意的\(n∈N*\)都有\(1\leqslant λT_{n}- \dfrac {d_{n}}{b_{2n}} < 2\)成立?若存在,求出\(λ\)的值;若不存在,说明理由.
  • 题型:解答题 题类:模拟题 难易度:中档

    年份:2020

    已知等比数列\(\{a _{n} \}\)的前\(n\)项和为\(S _{n}\),且\(a _{1} =m\),\(a _{n+1} =S _{n} +1(n∈N ^{*} ).\)
    \((1)\)求实数\(m\)的值和数列\(\{a _{n} \}\)的通项公式;
    \((2)\)设\(b _{n} = \begin{cases} {a_{n}(n\text{为奇数})} \\ {\log _{2}a_{n}(n\text{为偶数})}\end{cases}(n∈N^{*})\),求数列\(\{b _{n} \}\)的前\(2n\)项和\(T _{2n}\).