JEE Main & Advanced Sample Paper JEE Main - Mock Test - 32

  • question_answer
    If \[{{a}_{1}},{{a}_{2}},.....{{a}_{n}}\] are positive real numbers whose product is a fixed number c, then the minimum value of \[{{a}_{1}}+{{a}_{2}}+....+{{a}_{n-1}}+2{{a}_{n}}\] is -

    A) \[n{{(2C)}^{1/n}}\]     

    B)        \[\left( n+1 \right){{c}^{1/n}}\]

    C) \[2n{{c}^{1/n}}\]            

    D)        \[(n+1){{\left( 2c \right)}^{1/n}}\]

    Correct Answer: A

    Solution :

    [a] \[A\ge G\] \[\frac{{{a}_{1}}+{{a}_{2}}+{{a}_{3}}+.....+{{a}_{n-1}}+2{{a}_{n}}}{n}\] \[\ge \sqrt[n]{{{a}_{1}}.{{a}_{2}}.{{a}_{3}}.....{{a}_{n-1}}2{{a}_{n}}}\] \[{{a}_{1}}+{{a}_{2}}+....+{{a}_{n-1}}+2{{a}_{n}}\ge n.{{\left( 2c \right)}^{1/n}}\]   


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