JEE Main & Advanced JEE Main Paper (Held on 10-4-2019 Afternoon)

  • question_answer
    If the tangent to the curve \[y=\frac{x}{{{x}^{2}}-3},x\in R,\]\[\left( x\ne \pm \sqrt{3} \right),\]at a point \[(\alpha ,\beta )\ne (0,0)\] on it is parallel to the line \[2x+6y11=0,\]then : [JEE Main 10-4-2019 Afternoon]

    A) \[|6\alpha +2\beta |=19\]

    B) \[|2\alpha +6\beta |=11\]

    C) \[|6\alpha +2\beta |=9\]       

    D) \[|2\alpha +6\beta |=19\]

    Correct Answer: A

    Solution :

                \[{{\left. \frac{dy}{dx} \right|}_{\left( \alpha ,\beta  \right)}}=\frac{-{{\alpha }^{2}}-3}{{{\left( {{\alpha }^{2}}-3 \right)}^{2}}}\] Given that : \[\frac{-{{\alpha }^{2}}-3}{{{\left( {{\alpha }^{2}}-3 \right)}^{2}}}=-\frac{1}{3}\]\[\Rightarrow \alpha =0,\pm 3\]\[(\alpha \ne 0)\] \[\Rightarrow \beta =\pm \frac{1}{2}.\]                     \[(\beta \ne 0)\] \[|6\alpha +2\beta |=19\]


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