JEE Main & Advanced Mathematics Relations Question Bank Mock Test - Relations and Functions

  • question_answer
    The domain of the function \[f(x)={{\left[ {{\log }_{10}}\left( \frac{5x-{{x}^{2}}}{4} \right) \right]}^{1/2}}\]is

    A) \[-\infty <x<\infty \]      

    B) \[1\le x\le 4\]

    C) \[4\le x\le 16\]    

    D) \[-1\le x\le 3\]

    Correct Answer: B

    Solution :

    [b] We have \[f(x)={{\left[ {{\log }_{10}}\left( \frac{5x-{{x}^{2}}}{4} \right) \right]}^{1/2}}\]...(1) From (1), clearly, \[f(x)\]is defined for those values of x for which \[\log \left[ \frac{5x-{{x}^{2}}}{4} \right]\ge 0\] Or  \[\left( \frac{5x-{{x}^{2}}}{4} \right)\ge 10{}^\circ \] Or  \[\left( \frac{5x-{{x}^{2}}}{4} \right)\ge 1\] Or  \[{{x}^{2}}-5x+4\le 0\] Or  \[(x-1)(x-4)\le 0\] Hence, the domain of the functions is [1, 4].


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