SSC Sample Paper SSC CHSL (10+2) Sample Test Paper-7

  • question_answer
    .If \[x+\frac{1}{x}=\sqrt{3}\] , find the value of \[{{x}^{24}}+{{x}^{18}}\]

    A)  0                                

    B)  1

    C)  2                                

    D) \[-\,2\]

    Correct Answer: A

    Solution :

     \[x+\frac{1}{x}=\sqrt{3}\] On squaring both sides, \[{{x}^{2}}+\frac{1}{{{x}^{2}}}+2=3\] \[\Rightarrow \]\[{{x}^{2}}+\frac{1}{{{x}^{2}}}=1\] \[\Rightarrow \]\[{{x}^{4}}-{{x}^{2}}+1=0\] \[\therefore \] \[{{x}^{24}}+{{x}^{18}}={{x}^{18}}({{x}^{6}}+1)\] \[={{x}^{18}}({{({{x}^{2}})}^{3}}+{{1}^{3}})\]             \[={{x}^{18}}({{x}^{2}}+1)({{x}^{4}}-{{x}^{2}}+1)=0\]


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