JEE Main & Advanced Mathematics Differentiation Question Bank Self Evaluation Test - Limits and Derivatives

  • question_answer
    If \[y=\frac{1}{1+{{x}^{\beta -\alpha }}+{{x}^{\gamma -\alpha }}}+\frac{1}{1+{{x}^{\alpha -\beta }}+{{x}^{\gamma -\beta }}}+\frac{1}{1+{{x}^{\alpha -\gamma }}+{{x}^{\beta -\gamma }}}\]then \[\frac{dy}{dx}\] is equal to

    A) 0

    B) 1

    C) \[(\alpha +\beta +\gamma ){{x}^{\alpha +\beta +\gamma -1}}\]

    D) None of these

    Correct Answer: A

    Solution :

    [a] we have, \[y=\frac{1}{1+\frac{{{x}^{\beta }}}{{{x}^{\alpha }}}+\frac{{{x}^{\gamma }}}{{{x}^{\alpha }}}}+\frac{1}{1+\frac{{{x}^{\alpha }}}{{{x}^{\beta }}}+\frac{{{x}^{\gamma }}}{{{x}^{\beta }}}}+\frac{1}{1+\frac{{{x}^{\alpha }}}{{{x}^{\gamma }}}+\frac{{{x}^{\beta }}}{{{x}^{\gamma }}}}\] \[=\frac{{{x}^{\alpha }}}{{{x}^{\alpha }}+{{x}^{\beta }}+{{x}^{\gamma }}}+\frac{{{x}^{\beta }}}{{{x}^{\alpha }}+{{x}^{\beta }}+{{x}^{\gamma }}}+\frac{{{x}^{\gamma }}}{{{x}^{\alpha }}+{{x}^{\beta }}+{{x}^{\gamma }}}\] \[=\frac{{{x}^{\alpha }}+{{x}^{\beta }}+{{x}^{\gamma }}}{{{x}^{\alpha }}+{{x}^{\beta }}+{{x}^{\gamma }}}=1\] \[\therefore \frac{dy}{dx}=0.\]


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