JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation of implicit function Parametric

  • question_answer
    If \[{{x}^{3}}+{{y}^{3}}-3axy=0\], then \[\frac{dy}{dx}\] equals          [RPET 1996]

    A)  \[\frac{ay-{{x}^{2}}}{{{y}^{2}}-ax}\]

    B)  \[\frac{ay-{{x}^{2}}}{ay-{{y}^{2}}}\]

    C)  \[\frac{{{x}^{2}}+ay}{{{y}^{2}}+ax}\]

    D)   \[\frac{{{x}^{2}}+ay}{ax-{{y}^{2}}}\]

    Correct Answer: A

    Solution :

               \[{{x}^{3}}+{{y}^{3}}-3axy=0\]            Differentiate w.r.t. x,            \[3{{x}^{2}}+3{{y}^{2}}.\frac{dy}{dx}-3a\left( x\frac{dy}{dx}+y \right)=0\]            \[3({{x}^{2}}-ay)+3\frac{dy}{dx}({{y}^{2}}-ax)=0\]\[\Rightarrow \]\[\frac{dy}{dx}=\frac{ay-{{x}^{2}}}{{{y}^{2}}-ax}\].


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