共50条信息
已知等比数列\(\{a_{n}\}\)的公比\(q > 1\),\(a_{1}=1\),且\(2a_{2}\),\(a_{4}\),\(3a_{3}\)成等差数列.
\((1)\)求数列\(\{a_{n}\}\)的通项公式;
\((2)\)记\(b_{n}=2na_{n}\),求数列\(\{b_{n}\}\)的前\(n\)项和\(T_{n}\).
等差数列\(\left\{ {{a}_{n}} \right\}\)中,\({{a}_{5}}=1,{{a}_{1}}+{{a}_{7}}+{{a}_{10}}={{a}_{4}}+{{a}_{6}}\),则\({{S}_{10}}=(\) \()\)
已知数列\(\{a\)\({\,\!}_{n}\)\(\}\)是等差数列,\({{b}_{n}}=\dfrac{{{a}_{1}}+{{a}_{2}}+\ldots +{{a}_{n}}}{n}\)\((n=1,2,3,…)\).
证明:数列\(\{b_{n}\}\)是等差数列.
设等差数列\(\{a_{n}\}\)的前\(n\)项的和为\(S_{n}\),且\(S_{13}=52\),则\(a_{4}+a_{8}+a_{9}=(\) \()\)
已知数列\(\{{{a}_{n}}\}\)中,\({{a}_{1}}=1\),\(a_{n+1}^{{}}=a_{n}^{{}}+3\),则\({{a}_{6}}=(\) \()\)
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