CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2002

  • question_answer
    The equation of the tangent to the curve \[(1+{{x}^{2}})y=2-x\]where it crosses the\[x-\]axis, is:

    A) \[x+5y=2\]         

    B)                         \[x-5y=2\]

    C)                         \[5x-y=2\]         

    D)                         \[5x+y-2=0\]

    E)                         \[x-5y=0\]

    Correct Answer: A

    Solution :

    The   given   equation   of   curve   is\[(1+{{x}^{2}})y=2-x,\]it meets\[x-\]axis at (2, 0) Or it can be rewritten as\[y=\frac{2-x}{1+{{x}^{2}}}\] On differentiating w.r.t.\[x,\]we get \[\frac{dy}{dx}=\frac{(1+{{x}^{2}})(-1)-(2-x)(2x)}{{{(1+{{x}^{2}})}^{2}}}\]                 \[=\frac{-1-{{x}^{2}}-4x+2{{x}^{2}}}{{{(1+{{x}^{2}})}^{2}}}\] \[{{\left( \frac{dy}{dx} \right)}_{(2,0)}}=\frac{-1-4-8+8}{25}=-\frac{1}{5}\] \[\therefore \]Required equation of tangent is \[(y-0)=-\frac{1}{5}(x-2)\] \[\Rightarrow \]               \[x+5y=2\]


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