JEE Main & Advanced Mathematics Sequence & Series Question Bank Geometric Progression

  • question_answer
    If \[{{\log }_{x}}a,\ {{a}^{x/2}}\] and \[{{\log }_{b}}x\] are in G.P., then \[x=\]

    A) \[-\log ({{\log }_{b}}a)\]

    B) \[-{{\log }_{a}}({{\log }_{a}}b)\]

    C)  \[{{\log }_{a}}({{\log }_{e}}a)-{{\log }_{a}}({{\log }_{e}}b)\]

    D)   \[{{\log }_{a}}({{\log }_{e}}b)-{{\log }_{a}}({{\log }_{e}}a)\]

    Correct Answer: C

    Solution :

    Obviously \[{{({{a}^{x/2}})}^{2}}={{\log }_{x}}a\ .\ {{\log }_{b}}x={{\log }_{b}}a\] \[\Rightarrow \]\[{{a}^{x}}={{\log }_{b}}a\]\[\Rightarrow \]\[x={{\log }_{a}}({{\log }_{b}}a)\] \[\Rightarrow \]\[x={{\log }_{a}}\left( \frac{{{\log }_{e}}a}{{{\log }_{e}}b} \right)={{\log }_{a}}({{\log }_{e}}a)-{{\log }_{a}}({{\log }_{e}}b)\].


You need to login to perform this action.
You will be redirected in 3 sec spinner