JEE Main & Advanced Mathematics Equations and Inequalities Question Bank Self Evaluation Test - Linear Inequalities

  • question_answer
    The number of real values of parameter k for which \[{{(lo{{g}_{16}}x)}^{2}}-{{\log }_{16}}x+{{\log }_{16}}k=0\] will have exactly one solution is

    A) 0

    B) 2

    C) 1

    D) 4

    Correct Answer: C

    Solution :

    [c] The equation is \[{{(lo{{g}_{16}}x)}^{2}}-{{\log }_{16}}x+{{\log }_{16}}k=0\] Clearly \[x>0\] Solving the equation, we get \[{{\log }_{16}}x=\frac{1\pm \sqrt{1-4(lo{{g}_{16}}k)}}{2}\] For exactly one solution \[1-4{{\log }_{16}}k=0\] \[\Rightarrow {{k}^{4}}=16\Rightarrow k=\pm 2\][Taking real values] Now \[{{\log }_{16}}k\]is defined if \[k>0\Rightarrow k=2\]


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