BCECE Engineering BCECE Engineering Solved Paper-2003

  • question_answer
    If \[y={{x}^{2}}+\frac{1}{{{x}^{2}}+\frac{1}{{{x}^{2}}+\frac{1}{{{x}^{2}}+...\infty }}}\,\,,\]then  \[\frac{dy}{dx}\]is equal to:

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

    B)                   \[\frac{xy}{y+{{x}^{2}}}\]

    C)                   \[\frac{xy}{y-{{x}^{2}}}\]                            

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

    Correct Answer: A

    Solution :

    Since, \[y={{x}^{2}}+\frac{1}{{{x}^{2}}+\frac{1}{{{x}^{2}}\frac{1}{{{x}^{2}}+...\infty }}}\] \[\Rightarrow \]               \[y={{x}^{2}}+\frac{1}{y}\] \[\Rightarrow \]               \[{{y}^{2}}={{x}^{2}}y+1\] On differentiating both sides w.r.t. \[x,\]we get \[2y\frac{dy}{dx}={{x}^{2}}\frac{dy}{dx}+2xy+0\] \[\Rightarrow \]               \[\frac{dy}{dx}=\frac{2xy}{2y-{{x}^{2}}}\]


You need to login to perform this action.
You will be redirected in 3 sec spinner