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9th Class Mathematics Number System and its Operations Question Bank Number Systems

  • question_answer
    If\[x=7+4\sqrt{3}\]and\[xy=1\], what is the value of\[\frac{1}{{{x}^{2}}}+\frac{1}{{{y}^{2}}}\]?

    A) \[64\]                            

    B) \[134\]              

    C) \[194\]              

    D)        \[1/49\]             

    Correct Answer: C

    Solution :

    \[x=\frac{1}{y}=7+4\sqrt{3}.y=\frac{1}{x}=7-4\sqrt{3}\] \[\frac{1}{{{x}^{2}}}+\frac{1}{{{y}^{2}}}={{x}^{2}}+{{y}^{2}}=194\]


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