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

  • question_answer
    If x + y \[=3\sqrt{8}\]  x - y \[=\sqrt{2}\] then the value of \[8xy\,\,({{x}^{2}}+{{y}^{2}})\] is

    A)  5760                           

    B)  5440

    C)  5360                           

    D)  5180

    Correct Answer: D

    Solution :

     \[2({{x}^{2}}+{{y}^{2}})\] \[=(x+{{y}^{2}})+{{(x-y)}^{2}}\] \[={{(3\sqrt{8})}^{2}}+{{(\sqrt{2\,})}^{2}}\] \[=72+2=74\] \[4xy={{(x+y)}^{2}}-{{(x-y)}^{2}}\] \[={{(3\sqrt{8})}^{2}}-{{(\sqrt{2})}^{2}}=72-2=70\] \[\therefore \] \[8xy({{x}^{2}}+{{y}^{2}})=4xy.2({{x}^{2}}+{{y}^{2}})\] \[=70\times 74=5180\]


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