SSC Sample Paper SSC CHSL (10+2) Sample Test Paper-2

  • question_answer
    If\[x=\sqrt{6}+\sqrt{5}\]then\[{{x}^{2}}+\frac{1}{{{x}^{2}}}-2=?\]

    A) \[2\sqrt{6}\]                              

    B) \[2\sqrt{5}\]

    C) \[20\]                  

    D)        \[24\]

    Correct Answer: C

    Solution :

    \[x=\sqrt{6}+\sqrt{5}\] \[\therefore \]\[\frac{1}{x}=\frac{1}{\sqrt{6}+\sqrt{5}}\] \[=\frac{(\sqrt{6}-\sqrt{5})}{(\sqrt{6}+\sqrt{5})(\sqrt{6}-\sqrt{5})}=\sqrt{6}-\sqrt{5}\] \[\therefore \]      \[({{x}^{2}}+\frac{1}{{{x}^{2}}}-2)={{(x-\frac{1}{x})}^{2}}\]


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