优优班--学霸训练营 > 知识点挑题
全部资源
          排序:
          最新 浏览

          50条信息

            • 1.

              若实数\(x+y+z=1\),则\(2x^{2}+y^{2}+3z^{2}\) 的最小值为\((\)  \()\)

              A.\(1\)     
              B.\(\dfrac{2}{3} \)
              C.\(\dfrac{6}{11} \)
              D.\(11\)
            • 2.

              已知\(a{,}b{,}c{∈}(0{,}1)\),且\({ab}{+}{bc}{+}{ac}{=}1\),则\(\dfrac{1}{1{-}a}{+}\dfrac{1}{1{-}b}{+}\dfrac{1}{1{-}c}\)的最小值为\(({  })\)

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

              已知\(x\),\(y\),\(z∈R\),且\(\dfrac{1}{x}+\dfrac{2}{y}+\dfrac{3}{z}=1\),则\(x+\dfrac{y}{2}+\dfrac{z}{3}\)的最小值是\((\)    \()\)

              A.\(5\)
              B.\(6\)
              C.\(8\)
              D.\(9\)
            • 4.

              已知\(x+y=1\),则\(2{{x}^{2}}+3{{y}^{2}}\)的最小值是\((\)       \()\)

              A.\(\dfrac{5}{6}\)
              B.\(\dfrac{6}{5}\)
              C.\(\dfrac{25}{36}\)
              D.\(\dfrac{36}{25}\)
            • 5.

              设\(x > y > z > 0\),若\(\dfrac{1}{x-y}+\dfrac{1}{y-z}+\dfrac{\lambda }{z-x}\geqslant 0\)恒成立,则\(λ\)的最大值是\((\)    \()\)

              A.\(1\)
              B.\(2\)
              C.\(3\)
              D.\(4\)
            • 6.

              设\(a_{1}\),\(a_{2}\),\(…\),\(a_{n}∈R\),\(n∈N^{*}\)且\(n\geqslant 3.\)若\(p\):\(a_{1}\),\(a_{2}\),\(…\),\(a_{n}\)成等比数列;\(q\):\((a_{1}^{2}+a_{2}^{2}+…+a_{n-1}^{2})(a_{2}^{2}+a_{3}^{2}+…+a_{n}^{2})=(a_{1}a_{2}+a_{2}a_{3}+…+a_{n-1}a_{n})^{2}\),则\((\)  \()\)

              A.\(p\)是\(q\)的充分条件,但不是\(q\)的必要条件
              B.\(p\)是\(q\)的必要条件,但不是\(q\)的充分条件
              C.\(p\)是\(q\)的充分必要条件
              D.\(p\)既不是\(q\)的充分条件,也不是\(q\)的必要条件
            • 7. 已知\(2x+3y+4z=1\),则\(x^{2}+y^{2}+z^{2}\)的最小值是\((\)  \()\)
              A.\( \dfrac {1}{9}\)
              B.\( \dfrac {1}{13}\)
              C.\( \dfrac {1}{21}\)
              D.\( \dfrac {1}{29}\)
            • 8. 已知\(x^{2}+y^{2}+z^{2}=2\),则\(3x+4y+5z\)的最大值为(    )
              A.\(12\)           
              B.\(24\)        
              C.\(10\)          
              D.\(100\)
            • 9.

              若实数\(x\)\(y\)\(z\)满足\({x}^{2}+{y}^{2}+{z}^{2}=9 \),则\(x+2y+3z \)的最大值是 \((\)     \()\)

              A.\(126\)            
              B.\(3\sqrt{14}\)
              C.\(\dfrac{14}{9}\)
              D.\(\dfrac{\sqrt{14}}{3}\) 
            • 10.

              设\(c_{1}\),\(c_{2}\),\(…\),\(c_{n}\)是\(a_{1}\),\(a_{2}\),\(…\),\(a_{n}\)的某一排列\((a_{1},a_{2},…,a_{n}\)均为正数\()\),则\( \dfrac{a_{1}}{c_{1}}+ \dfrac{a_{2}}{c_{2}}+…+ \dfrac{a_{n}}{c_{n}}\)的最小值是

              A.\(2n\)
              B.\( \dfrac{1}{n}\)
              C.\( \sqrt{n}\)
              D.\(n\)
            0/40

            进入组卷