JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2011

  • question_answer
        On the curve\[{{x}^{3}}=12y,\]the abscissa changes at a faster rate than the ordinate. Then,\[x\]belongs to the interval

    A)  \[(-2,2)\]            

    B)  \[(-1,1)\]

    C)  (0, 2)                                    

    D)  None of these

    Correct Answer: A

    Solution :

                    Given, \[{{x}^{3}}=12y\] \[\Rightarrow \]               \[3{{x}^{2}}\frac{dx}{dy}=12\] \[\Rightarrow \]               \[\frac{dx}{dy}=\frac{4}{{{x}^{2}}}\] But it is given \[\left| \frac{dy}{dx} \right|>1\] \[\therefore \]  \[\frac{4}{{{x}^{2}}}>1\] \[\Rightarrow \]               \[{{x}^{2}}-4<0\] \[\Rightarrow \]               \[-2<x<2\]


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