优优班--学霸训练营 > 知识点挑题
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            • 1.

              \(\sqrt{({3}-a)(a+{6})}(-{6}\leqslant a\leqslant {3})\)的最大值为  \((\)    \()\)

              A.\(9\)
              B.\(\dfrac{{9}}{{2}}\)
              C.\(3\)
              D.\(\dfrac{{3}\sqrt{{2}}}{{2}}\)
            • 2.

              已知\(a > 0\),\(ab=1\),则\(\dfrac{{{a}^{2}}+{{b}^{2}}}{a-b}\)的最小值是\((\)    \()\)

              A.\(2\sqrt{2}\)
              B.\(\sqrt{2}\)
              C.\(2\)
              D.\(1\)
            • 3.

              已知\(x{ > }2\),函数\(y{=}\dfrac{4}{x{-}2}{+}x\)的最小值是\((\)  \()\)

              A.\(5\)                                
              B.\(4\)                                
              C.\(6\)                                
              D.\(8\)
            • 4.

              某粮油店一年需购买食用油\(900\)吨,每次都购买\(x\)吨,运费为\(3\)千元\(/\)次,一年的总存储费用为\(3x\)千元,要使一年的总运费与总存储费用之和最小,则\(x\)的值为

              A.\(10\)
              B.\(20\)
              C.\(30\)
              D.\(40\)
            • 5.

              若\(a\),\(b\)都是正数,则\(\left( 1+\dfrac{b}{a} \right)\left( 1+\dfrac{4a}{b} \right)\)的最小值为\((\)    \()\)

              A.\(7\)
              B.\(8\)
              C.\(9\)
              D.\(10\)
            • 6.

              已知函数\(f(x)=|\lg x|\),\(a > b > 0\),\(f(a)=f(b)\),则\(\dfrac{{a}^{2}+{b}^{2}}{a-b} \)的最小值等于    \((\)    \()\)

              A.\(2\sqrt{2}\)
              B.\(\sqrt{5}\)
              C.\(2+\sqrt{3}\)
              D.\(2\sqrt{3}\)
            • 7.

              若以椭圆上一点和两个焦点为顶点的三角形的最大面积为\(1\),则长轴长的最小值为 (    )

              A.\(1\)              
              B.\(\sqrt{2}\)
              C.\(2\)
              D.\(2\sqrt{2}\)
            • 8.

              若一组数据\(2\),\(4\),\(6\),\(8\)的中位数、方差分别为\(m\)\(n\),且\(ma+nb=\)\(1(\)\(a > \)\(0\),\(b > \)\(0)\),则\( \dfrac{1}{a}+ \dfrac{1}{b} \)的最小值为\((\) \()\)

              A.\(6\) \(+\)\(2 \sqrt{3} \)
              B.\(4\) \(+\)\(3 \sqrt{5} \)
              C.\(9\) \(+\)\(4 \sqrt{5} \)
              D.\(20\)
            • 9.

              已知\(k∈R\),直线\(l_{1}\):\(x+ky=0\)过定点\(P\),直线\(l_{2}\):\(kx-y-2k+2=0\)过定点\(Q\),两直线交于点\(M\),则\(|MP|+|MQ|\)的最大值是\((\)   \()\)

              A.\(2\sqrt{2}\)
              B.\(4\)
              C.\(4\sqrt{2}\)
              D.\(8\)
            • 10.

              ​\( \dfrac{1}{2-{\cos }^{2}θ}+ \dfrac{1}{2-{\sin }^{2}θ} (\)\(θ\)\(∈R)\)的最小值为\((\) \()\)

              A.\( \dfrac{4}{3} \)
              B.\( \dfrac{3}{4} \)
              C.\( \dfrac{2}{3} \)
              D.\( \dfrac{3}{2} \)
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