12th Class Mathematics Applications of Derivatives Question Bank Case Based (MCQs) - Derivatives

  • question_answer
    If \[x={{e}^{x/y}}\], then find \[\frac{dy}{dx}\].

    A) \[-\frac{\left( x+y \right)}{x\,\log \,x}\]

    B) \[-\frac{\left( x-y \right)}{x\,\log \,x}\]

    C) \[\frac{\left( x+y \right)}{x\,\log \,x}\]

    D) \[\frac{\left( x-y \right)}{x\,\log \,x}\]

    Correct Answer: D

    Solution :

    Given \[x={{e}^{x/y}}\] \[\Rightarrow \,\log \,x=\frac{x}{y}\log e\Rightarrow y\log x=x\] \[\Rightarrow \,y\frac{1}{x}+\left( \log x \right)\frac{dy}{dx}=1\] \[\Rightarrow \,\frac{dy}{dx}=\left( 1-\frac{y}{x} \right)\frac{1}{\log \,x}\Rightarrow \frac{1}{x\log \,x}\left( x-y \right)\]


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