共50条信息
设\({S}_{n} \)是数列\(\left\{{a}_{n}\right\} \)的前\(n\)项和,且\({a}_{1}=1,{a}_{n+1}=-{S}_{n}{S}_{n+1} \),则使\(\dfrac{nS_{n}^{2}}{1+10S_{n}^{2}} \)取得最大值时\(n\)的值为 \((\) \()\)
已知\(f\left( \left. x+ \dfrac{1}{x} \right. \right)=x^{2}+ \dfrac{1}{x^{2}}\),则\(f(x)\)的解析式为________.
\((1)\)已知\(x < -2\),求函数\(y=2x+ \dfrac{1}{x+2}\)的最大值;
\((2)\)求\(y= \dfrac{x^{2}+5}{ \sqrt{x^{2}+4}}\)的最小值;
\((3)\)若正数\(a\),\(b\)满足\(ab=a+b+3\),求\(a+b\)的取值范围.
已知函数\(f(x)=x+\dfrac{4}{x} \),\(g(x)=2^{x}+a\),若\(∀x_{1}∈\left[ \dfrac{1}{2},1\right] \),\(∃x_{2}∈[2,3]\),使得\(f(x_{1})\geqslant g(x_{2})\),则实数\(a\)的取值范围是\((\) \()\)
设\(f(x)=\begin{cases} {{(x-a)}^{2}},x\leqslant 0 \\ x+\dfrac{1}{x}+a,x > 0 \end{cases}\) ,若\(f(0)\)是\(f(x)\)的最小值,则\(a\)的取值范围为\((\) \()\)
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