优优班--学霸训练营 > 知识点挑题
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            • 1.

              若曲线\(y=f(x)=\ln x+ax^{2}(a\)为常数\()\)不存在斜率为负数的切线,则实数\(a\)的取值范围是\((\)  \()\)

              A.\(\left( \left. - \dfrac{1}{2},+∞ \right. \right)\)
              B.\(\left[ \left. - \dfrac{1}{2},+∞ \right. \right) \)

              C.\((0,+∞)\)                                              
              D.\([0,+∞)\)
            • 2.

              若存在实常数\(k\)和\(b\),使得函数\({F}\left( x \right)\)和\({G}\left( x \right)\)对其公共定义域上的任意实数\(x\)都满足:\(F\left( x \right)\geqslant kx+b\)和\(G\left( x \right)\leqslant kx+b\)恒成立,则称此直线\(y=kx+b\)为\(F\left( x \right)\)和\(G\left( x \right)\)的“隔离直线”,已知函数\(f\left( x \right)={{x}^{2}}\left( x\in R \right)\),\(g\left( x \right)=\dfrac{1}{x}\left( x < 0 \right),h\left( x \right)=2e\ln x\),有下列命题:

              \(①F\left( x \right)=f\left( x \right)-g\left( x \right)\)在\(x\in \left( -\dfrac{1}{\sqrt[3]{2}},0 \right)\)内单调递增;

              \(②f\left( x \right)\)和\(g\left( x \right)\)之间存在“隔离直线”,且\({b}\)的最小值为\(-4\);

              \(③f\left( x \right)\)和\(g\left( x \right)\)之间存在“隔离直线”,且\(k\)的取值范围是\((-4,0] \);

              \(④f\left( x \right)\)和\(h\left(x\right) \)之间存在唯一的“隔离直线”\(y=2 \sqrt{e}x-e \).

              其中真命题的个数有\((\)    \()\)

              A.\(1\)个
              B.\(2\)个  
              C.\(3\)个   
              D.\(4\)个
            • 3.
              已知函数\(f(x)=\)\( \dfrac{1+\ln x}{x}\)
              \((1)\)若函数\(f(x)\)在区间\((a,a+\)\( \dfrac{1}{2}\) \()\)上存在极值,求正实数\(a\)的取值范围;
              \((2)\)若当\(x\geqslant 1\)时,不等式\(f(x)\geqslant \)\( \dfrac{k}{x+1}\) 恒成立,求实数\(k\)的取值范围.
            • 4. 已知函数\(f(x)=x^{3}+(1-a)x^{2}-a(a+2)x+b(a,b∈R)\).

              \((1)\)若函数\(f(x)\)的图象过原点,且在原点处的切线斜率为\(-3\),求\(a\),\(b\)的值;

              \((2)\)若曲线\(y=f(x)\)存在两条垂直于\(y\)轴的切线,求\(a\)的取值范围.

            • 5.

              已知函数\(f\left( x \right)=\dfrac{\ln x+{{\left( x-b \right)}^{2}}}{x}\left( b\in R \right)\) ,若存在\(x\in \left[ \dfrac{1}{2},2 \right]\),\(使得f\left(x\right)+x{f}^{{{{"}}}}\left(x\right) > 0 \) ,则实数\(b\)的取值范围是\((\)   \()\)

              A.\((-∞, \dfrac{3}{2} )\)
              B.\((-∞, \dfrac{9}{4} )\)              
              C.\((-∞,3 )\)                
              D.\((-∞, \sqrt{2} )\)
            • 6.

              若曲线\(f(x)=\ln x+ax\)\({\,\!}^{2}\)\((a\)为常数\()\)不存在斜率为负数的切线,则实数\(a\)的取值范围是________.

            • 7. 如果曲线\(y=x^{3}+x-10\)的某一切线与直线\(y=4x+3\)平行,求切点坐标与切线方程.
            • 8. 若曲线\(y=x^{4}\)的一条切线\(l\)与直线\(x+4y-8=0\)垂直,则\(l\)的方程为\((\)  \()\)
              A.\(4x-y-3=0\)
              B.\(x+4y-5=0\)
              C.\(4x-y+3=0\)
              D.\(x+4y+3=0\)
            • 9.

              已知\(f\left( x \right)=a\ln x-{{x}^{2}}\)在区间\(\left( 0,1 \right)\)内任取两个不相等的实数\(p\),\(q\),不等式\(\dfrac{f\left( p \right)-f\left( q \right)}{p-q} > 1\)恒成立,则实数\(a\)的取值范围为                                                       \((\)    \()\)

              A.\(\left( 3,5 \right)\)
              B.\(\left( -\infty ,3 \right]\)
              C.\(\left( 3,5 \right]\)
              D.\(\left[ 3,+\infty \right)\)
            • 10.

              定义在区间\(\left[ a,b \right]\)上的连续函数\(y=f\left( x \right)\),如果\(\exists \xi \in \left[ a,b \right]\),使得\(f\left( b \right)-f\left( a \right)={f}{{{'}}}\left( \xi \right)\left( b-a \right)\),则称\(\xi \)为区间\(\left[ a,b \right]\)上的“中值点”,下列函数:\(①f\left( x \right)=3x+2\);\(②f\left( x \right)={{x}^{2}}-x+1\);\(③f\left( x \right)={\ln }\left( x+1 \right)\);\(④f\left( x \right)={{\left( x-\dfrac{1}{2} \right)}^{3}}\)中,在区间\(\left[ 0,1 \right]\)上“中值点”多于一个的函数序号为__________\(.(\)写出所有满足条件的函数的序号\()\)

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