CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    The     domain     of     the     function \[f(x)={{\log }_{2}}({{\log }_{3}}({{\log }_{4}}x))\]is

    A)  \[(-\infty ,4)\]

    B)                         \[(4,\infty )\]

    C)  \[(0,4)\]             

    D)         \[(1,\infty )\]

    E)  \[(-\infty ,1)\]

    Correct Answer: B

    Solution :

    Given, \[f(x)={{\log }_{2}}({{\log }_{3}}({{\log }_{4}}x))\] We know\[{{\log }_{a}}x\]is positive, if\[x>a\] and\[{{\log }_{a}}x\]is negative, if \[x<a\] For\[f(x)\]to be defined \[{{\log }_{3}}{{\log }_{4}}x>0,{{\log }_{4}}x>0\]and \[x>0\] \[\Rightarrow \] \[{{\log }_{4}}x>{{3}^{0}}=1,x>{{4}^{0}}\]and \[x>0\] \[\Rightarrow \] \[x>4,x>1\]and \[x>0\] \[\Rightarrow \]               \[x>4\]


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