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

  • question_answer
    If \[G\] be the geometric mean of \[x\] and \[y\], then \[\frac{1}{{{G}^{2}}-{{x}^{2}}}+\frac{1}{{{G}^{2}}-{{y}^{2}}}=\]

    A) \[{{G}^{2}}\]

    B) \[\frac{1}{{{G}^{2}}}\]

    C) \[\frac{2}{{{G}^{2}}}\]

    D) \[3{{G}^{2}}\]

    Correct Answer: B

    Solution :

    As given \[G=\sqrt{xy}\] \[\therefore \]\[\frac{1}{{{G}^{2}}-{{x}^{2}}}+\frac{1}{{{G}^{2}}-{{y}^{2}}}=\frac{1}{xy-{{x}^{2}}}+\frac{1}{xy-{{y}^{2}}}\]                             \[=\frac{1}{x-y}\left\{ -\frac{1}{x}+\frac{1}{y} \right\}=\frac{1}{xy}=\frac{1}{{{G}^{2}}}\].


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