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JEE Main & Advanced Sample Paper JEE Main Sample Paper-9

  • question_answer
    If the ordered pair (x, y) lies on the circle \[{{x}^{2}}+{{y}^{2}}=9\] then the largest value of the expression \[{{x}^{2}}+2{{y}^{2}}+4x\]equals

    A)  22                         

    B)  27     

    C)  24                         

    D)  36

    Correct Answer: A

    Solution :

    Expression \[={{x}^{2}}+2{{y}^{2}}+4x=9+{{y}^{2}}+4x\] \[=9+9-{{x}^{2}}+4x=18-[{{x}^{2}}-4x]=18-[{{(x-)}^{2}}-4]\]\[=22-{{(x-2)}^{2}}\] \[\therefore \]Maximum value = 22


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