共50条信息
\((2)\)设\({{b}_{n}}=\dfrac{3}{{{a}_{n}}{{a}_{n+1}}}\),求数列\(\{{{b}_{n}}\}\)的前\(n\)项和\({{T}_{n}}\).
设数列\(\left\{ {{a}_{n}} \right\}\)前\(n\)项和为\({{s}_{n}}\),且\({{s}_{n}}=2{{a}_{n}}-2(n\in {{N}^{*}})\)
\((\)Ⅰ\()\)证明:数列\(\left\{ {{a}_{n}} \right\}\)是等比数列,并求出其通项公式;
\((\)Ⅱ\()\)证明:数列\(\left\{ {{a}_{n}} \right\}\)中不可能存在三项成等差.
已知\(\{a_{n}\}\)是等比数列,\(a_{1}=1\),\(a_{4}=8\),\(\{b_{n}\}\)是等差数列,\(b_{1}=3\),\(b_{4}=12\),
\((1)\)求\(\{a_{n}\}\)和\(\{b_{n}\}\)的通项公式;
\((2)\)设\(c_{n}=a_{n}+b_{n}\),求数列\(\{c_{n}\}\)的前\(n\)项和\(S_{n}\).
已知等差数列\(\left\{ {{a}_{n}} \right\}\)的前\(n\)项和\({{S}_{n}}\),满足\({{S}_{3}}=0,{{S}_{5}}=-5\),则数列\(\left\{ \dfrac{1}{{{a}_{2n-1}}{{a}_{2n+1}}} \right\}\)的前\(50\)项和\({{T}_{50}}=\) __________.
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