RAJASTHAN ­ PET Rajasthan PET Solved Paper-2002

  • question_answer
    If\[y=\sqrt{x+\sqrt{x+\sqrt{x+......\infty }}},\]then-y is equal to

    A)  \[\frac{x}{2y-1}\]

    B)  \[\frac{1}{2y-1}\]

    C)  \[\frac{2}{y-1}\]

    D)  None of these

    Correct Answer: B

    Solution :

     \[y=\sqrt{x+\sqrt{x+\sqrt{x+.....\infty }}}\] \[{{y}^{2}}=x+\sqrt{x+\sqrt{x+.....\infty }}\] \[\Rightarrow \] \[{{y}^{2}}=x+y\] On differentiating with respect to\[x,\] \[2y\frac{dy}{dx}=1+\frac{dy}{dx}\] \[\Rightarrow \] \[\frac{dy}{dx}(2y-1)=1\] \[\Rightarrow \] \[\frac{dy}{dx}=\frac{1}{2y-1}\]


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