SSC Sample Paper SSC CGL - Sample Paper-4

  • question_answer
    If \[\sqrt{1-\sqrt{{{x}^{4}}-{{x}^{2}}}}=x-1,\] then what is the value of x?

    A)  \[\frac{-\,5}{4}\]                                  

    B)  \[\frac{5}{4}\]

    C)  \[\frac{1}{4}\]                         

    D)  \[\frac{-\,1}{4}\]

    Correct Answer: B

    Solution :

    \[\because \]       \[\sqrt{1-\sqrt{{{x}^{4}}-{{x}^{2}}}}=x-1\] Or         \[1-\sqrt{{{x}^{4}}-{{x}^{2}}}={{(x-1)}^{2}}\] Or         \[1-\sqrt{{{x}^{4}}-{{x}^{2}}}=({{x}^{2}}-2x+1)\] Or         \[-\sqrt{{{x}^{4}}-{{x}^{2}}}=({{x}^{2}}-2x)\] Or         \[{{x}^{4}}-{{x}^{2}}={{({{x}^{2}}-2x)}^{2}}\] Or         \[{{x}^{4}}-{{x}^{2}}={{x}^{4}}+4{{x}^{2}}-4{{x}^{3}}\] Or         \[4{{x}^{3}}-{{x}^{2}}-4{{x}^{2}}=0\] Or         \[4{{x}^{3}}-5{{x}^{2}}=0\] Or         \[{{x}^{2}}(4x-5)=0\] Or         \[x=0,\] \[\frac{5}{4}\]


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