优优班--学霸训练营 > 知识点挑题
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            • 1.

              已知\(f(x)\)是定义在\(R\)上的减函数,其导函数\({f}{{{"}}}(x)\)满足\(\dfrac{f(x)+x{f}{{{"}}}(x)}{{f}{{{"}}}(x)} < 1\),则下列结论中正确的是\((\)   \()\)

              A.\(f(x) > 0\)在\(R\)上恒成立                   
              B.\(f(x) < 0\)在\(R\)上恒成立          
              C.当且仅当\(x\in (-\infty ,1)\),\(f(x) < 0\)
              D.当且仅当\(x\in (1,+\infty )\),\(f(x) > 0\)
            • 2.

              已知函数\(f\)\((\)\(x\)\()\)是定义在\((0,\)\(+\)\(∞\)\()\)上的单调函数,且对任意的正数\(x\)\(y\)都有\(f\)\((\)\(xy\)\()\)\(=f\)\((\)\(x\)\()\)\(+f\)\((\)\(y\)\()\)若数列\(\{\)\(a_{n}\)\(\}\)的前\(n\)项和为\(S_{n}\),且满足\(f\)\((\)\(S_{n}+\)\(2)\)\(-f\)\((\)\(a_{n}\)\()\)\(=f\)\((3)(\)\(n\)\(∈N\)\({\,\!}^{*}\)\()\),则\(a_{n}\)等于\((\) \()\)

              A.\(2\) \({\,\!}^{n-}\)\({\,\!}^{1}\)
              B.\(n\)
              C.\(2\) \(n-\)\(1\)              
              D.\({\left( \dfrac{3}{2}\right)}^{n-1} \)
            • 3.

              函数\(f\left(x\right) \)对任意实数\(x\)都满足条件\(f\left(x+2\right)f\left(x\right)=1 \),若\(f\left(2\right)=2 \),则\(f\left(2016\right)= (\)   \()\)

              A.\( \dfrac{1}{2} \)
              B.\(2\)
              C.\( \dfrac{1}{2016} \)
              D.\(2016\)
            • 4. 已知函数\(g(x)=ax^{2}-(a+1)x+1\),\(f(x)\)是定义在\(R\)上的不恒为零的函数,且对于任意的\(x\),\(y∈R\)都满足:\(f(xy)=xf(y)+yf(x)\).
              \((1)\)求不等式\(g(x) < 0\)的解集;
              \((2)\)当\(a=1\)时,若 \(f(2)=g(2)+1\),设\(a_{n}=f(2^{n})(n∈N^{*})\),求数列\(\{a_{n}\}\)的通项公式;
              \((3)\)在\((2)\)的基础上,若\(b_{n}= \dfrac {n+2}{n+1}⋅ \dfrac {1}{a_{n}}\),数列\(\{b_{n}\}\)的前\(n\)项和为\(S_{n}.\)求证:\(S_{n} < 1\).
            • 5.
              已知定义域为\(R\)的函数\(f(x)\)满足\(f(a+b)=f(a)⋅f(b)(a,b∈R)\),且\(f(x) > 0.\)若\(f(1)= \dfrac {1}{3}\),则\(f(-2)\)等于\((\)  \()\)
              A.\( \dfrac {1}{3}\)
              B.\( \dfrac {1}{9}\)
              C.\(3\)
              D.\(9\)
            • 6.
              \(10\)、已知函数 的定义域为 ,当 时, ;当 时, ;当  时, 。则 \((\)    \()\)
              A.               
              B.               
              C.                
              D.
            • 7. 已知定义域为\(R\)的函数\(f (x)\)对任意实数\(x\),\(y\)满足\(f(x+y)+f(x-y)=2f (x)\cos y\),且\(f(0)=0\),\(f( \dfrac {\pi }{2})=1.\)给出下列结论:
              \(①f( \dfrac {\pi }{4})= \dfrac {1}{2}\)
              \(②f(x)\)为奇函数
              \(③f(x)\)为周期函数
              \(④f(x)\)在\((0,π)\)内为单调函数
              其中正确的结论是____________\(.(\) 填上所有正确结论的序号\()\).
            • 8.
              设函数\(y=f(x)\)的定义域为\(R\),并且满足\(f(x-y)=f(x)-f(y)\),且\(f(2)=1\),当\(x > 0\)时,\(f(x) > 0\).
              \((1)\)求\(f(0)\)的值;
              \((2)\)判断函数\(f(x)\)的单调性,并给出证明;
              \((3)\)如果\(f(x)+f(x+2) < 2\),求\(x\)的取值范围.
            • 9.

              定义在\((0,+∞)\)上函数\(f(x)\)满足\(f(x)+f(y)=f(xy)\),且当\(x > 1\)时,\(f(x) < 0\),若不等式对任意\(x\),\(y∈(0,+∞)\)恒成立,则实数\(a\)的取值范围是____________.

            • 10.
              已知函数\(f(x)\)对任意实数\(x\),\(y\)满足\(f(x+y)=f(x)+f(y)\),且\(f(1)\geqslant 2.\)若存在整数\(m\),使得\(f(-2)-m^{2}-m+4=0\),则\(m\)取值的集合为 ______ .
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