JEE Main & Advanced Mathematics Sequence & Series Question Bank Relation between AP., GP. and HP.

  • question_answer
    If \[{{\log }_{x}}y,\ {{\log }_{z}}x,\ {{\log }_{y}}z\] are in G.P. \[xyz=64\] and \[{{x}^{3}},\ {{y}^{3}},\ {{z}^{3}}\] are in A.P., then

    A) \[x=y=z\]

    B) \[x=4\]

    C) \[x,\ y,\,z\] are in G.P.

    D) All the above

    Correct Answer: D

    Solution :

    \[{{\log }_{x}}y,\ {{\log }_{z}}x,\ {{\log }_{y}}z\] are in G.P. \[\Rightarrow \]\[{{({{\log }_{z}}x)}^{2}}={{\log }_{x}}y\times {{\log }_{y}}z={{\log }_{x}}z=\frac{1}{{{\log }_{z}}x}\] \[\Rightarrow \]\[{{({{\log }_{z}}x)}^{3}}=1\]\[\Rightarrow \]\[z=x\] Also, we can show \[z=x=y=4\].


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