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            • 1. \(5.\) 在公差不为零的等差数列\(\{ \)\(a_{n}\)\(\}\)中, \(a\)\({\,\!}_{1}\), \(a\)\({\,\!}_{3}\), \(a\)\({\,\!}_{7}\)依次成等比数列,前\(7\)项和为\(35\),则数列\(\{ \)\(a_{n}\)\(\}\)的通项 \(a_{n}\)等于\((\)  \()\)

              A.\(n\)     
              B.\(n\)\(+ 1\)    
              C.\(2\) \(n\)\(-1\)      
              D.\(2\) \(n\)\(+1\)


            • 2. 已知\(\{a_{n}\}\)是等差数列,其前\(n\)项和为\(S_{n}\),\(\{b_{n}\}\)是等比数列\((b_{n} > 0)\),且\(a_{1}=b_{1}=2\),\(a_{3}+b_{3}=16\),\(S_{4}+b_{3}=34\).
              \((1)\)求数列\(\{a_{n}\}\)与\(\{b_{n}\}\)的通项公式;  
               \((2)\)记\(T_{n}\)为数列\(\{a_{n}b_{n}\}\)的前\(n\)项和,求\(T_{n}\).
            • 3.

              \(7\)月份,有一款新服装投入某市场销售,\(7\)月\(1\)日该款服装仅销售出\(3\)件,\(7\)月\(2\)日售出\(6\)件,\(7\)月\(3\)日售出\(9\)件,\(7\)月\(4\)日售出\(12\)件,以后每天售出的件数分别递增\(3\)件直到日销售量达到最大\((\)只有\(l\)天\()\)后,每天销售的件数开始下降,分别递减\(2\)件,到\(7\)月\(31\)日刚好售出\(3\)件.

                  \((1)\)问\(7\)月几号该款服装销售件数最多\(?\)其最大值是多少\(?\)

                  \((2)\)按规律,当该商场销售此服装达到\(200\)件时,社会上就开始流行,而日销售量连续下降并低于\(20\)件时,则不再流行,问该款服装在社会上流行几天\(?\)说明理由.

            • 4.

              已知等差数列\(\{a_{n}\}\)的公差不为\(0\),\(a_{1}=1\),且\(a_{2}\),\(a_{4}\),\(a_{8}\)成等比数列,设\(\{a_{n}\}\)的前\(n\)项和为\(S_{n}\),则\(S_{n}=\)

              A.\(\dfrac{n(n+1)}{2}\)
              B.\(\dfrac{{{(n+1)}^{2}}}{2}\)
              C.\(\dfrac{{{n}^{2}}+1}{2}\)
              D.\(\dfrac{n(n+3)}{4}\)
            • 5.

              设数列\(\{{{a}_{n}}\}\)是公差大于\(0\)的等差数列,\({{S}_{n}}\)为数列\(\{{{a}_{n}}\}\)的前\(n\)项和\(.\)已知\({{S}_{3}}=9\),且\(2{{a}_{1}}\)\({{a}_{3}}-1\)\({{a}_{4}}+1\)构成等比数列.

              \((1)\)求数列\(\{{{a}_{n}}\}\)的通项公式;

              \((2)\)若数列\(\{{{b}_{n}}\}\)满足\(\dfrac{{{a}_{n}}}{{{b}_{n}}}={{2}^{n-1}}(n\in {{N}^{*}})\),设\({{T}_{n}}\)是数列\(\{{{b}_{n}}\}\)的前\(n\)项和,证明\({{T}_{n}} < 6\).

              \((3)\)数列\(\{ c_{n}\}\)满足:\(c_{1}{=}2\),\(c_{n{+}1}{=}3c_{n}{-}2n{+}1\),求数列\(\{ c_{n}\}\)的通项公式。

            • 6.

              已知每项均是正整数的数列\({a}_{1},{a}_{2},{a}_{3},……,{a}_{100} \),其中等于\(i\)的项有\({k}_{i} \)个\((i=1,2,3……)\),设\({b}_{i}={k}_{1}+{k}_{2}+……+{k}_{j}(j=1,2,3……) \),\(g(m)={b}_{1}+{b}_{2}+……+{b}_{m}-100m(m=1,2,3……) \)

              \((1)\)设数列\({k}_{1}=40,{k}_{2}=30,{k}_{3}=20,{k}_{4}=10,{k}_{5}=……={k}_{100}=0 \),求\(g(1)\),\(g(2)\),\(g(3)\),\(g(4)\);

              \((2)\)若\({a}_{1},{a}_{2},{a}_{3},……,{a}_{100} \)中最大的项为\(50\),比较\(g(m)\),\(g(m+1)\)的大小;

              \((3)\)若\({a}_{1}+{a}_{2}+……+{a}_{100}=200 \),求函数\(g(m)\)的最小值.

            • 7.

              已知首项为\(\begin{matrix} & \dfrac{1}{2} \\ & \\ \end{matrix}\)的等比数列\(\{a\)\(n\)\(\}\)是递减数列,其前\(n\)项和为\(S_{n}\),且\(S_{1}+a_{1}\),\(S_{2}+a_{2}\),\(S_{3}+a_{3\;\;\;\;\;\;\;}\)成等差数列.

              \((\)Ⅰ\()\) 求数列\(\{a\)\(n\)\(\}\)的通项公式;

              \((\)Ⅱ\()\) 若\({b}_{n}={a}_{n}·{\log }_{2}{a}_{n} \)数列\(\{b_{n}\}\)的前\(n\)项和为\(T_{n}\),求满足不等式\( \dfrac{{T}_{n}+2}{n+2}\geqslant \dfrac{1}{16} \)的最大\(n\)值.

            • 8.

              已知数列\({ }\!\!\{\!\!{ }{{a}_{n}}{ }\!\!\}\!\!{ }\)的前\(n\)项和\({{S}_{n}}\),点\((n,{{S}_{n}})(n\in {{N}^{*}})\)在函数\(f(x)=\dfrac{1}{2}{{x}^{2}}+\dfrac{1}{2}x\)的图象上.

              \((1)\)求数列\({ }\!\!\{\!\!{ }{{a}_{n}}{ }\!\!\}\!\!{ }\)的通项公式;

              \((2)\)设数列\({ }\!\!\{\!\!{ }\dfrac{1}{{{a}_{n}}{{a}_{n+2}}}{ }\!\!\}\!\!{ }\)的前\(n\)项和为\({{T}_{n}}\),不等式\({{T}_{n}} > \dfrac{1}{3}{{\log }_{a}}(1-a)\)对任意正整数\(n\)恒成立,求实数\(a\)的取值范围.

            • 9. 已知\(\triangle ABC\)的三边分别为\(a\),\(b\),\(c\),且其中任意两边长均不相等,若\( \dfrac {1}{a}\),\( \dfrac {1}{b}\),\( \dfrac {1}{c}\)成等差数列.
              \((1)\)比较\( \sqrt { \dfrac {b}{a}}\)与\( \sqrt { \dfrac {c}{b}}\)的大小,并证明你的结论;
              \((2)\)求证:角\(B\)不可能是钝角.
            • 10. 已知数列\(\{a_{n}\}\)是公差不为\(0\)的等差数列,\(a_{1}+1\),\(a_{2}+1\),\(a_{4}+1\)成等比数列,且\(a_{2}+a_{3}=-12\),则\(a_{n}=\) ______ .
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