JEE Main & Advanced JEE Main Paper Phase-I (Held on 08-1-2020 Evening)

  • question_answer
    The length of the perpendicular from the origin, on the normal to the curve, \[{{x}^{2}}+2xy-3{{y}^{2}}=0\] at the point (2, 2) is   [JEE MAIN Held on 08-01-2020 Evening]

    A) \[2\sqrt{2}\]      

    B) \[\sqrt{2}\]

    C) \[4\sqrt{2}\]      

    D) \[2\]

    Correct Answer: A

    Solution :

    Given curve \[{{x}^{2}}+3xy-xy-3{{y}^{2}}=0\] \[\Rightarrow \]\[\left( x-y \right)\left( x+3y \right)=0\]  \[\Rightarrow y=x\text{ }and\text{ }y=-\frac{x}{3}\] \[\therefore \] Normal pass through (2, 2) and is perpendicular to line \[x-y=0\] Let normal is \[x+y+\lambda =0\]   \[\Rightarrow \text{ }\left| X=-4 \right|\] \[\therefore \] Perpendicular distance = \[\left| \frac{-4}{\sqrt{2}} \right|=2\sqrt{2}\]


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