JEE Main & Advanced JEE Main Paper (Held On 12-Jan-2019 Evening)

  • question_answer
    If a curve passes through the point (\[1,\text{ }-2\]) and has slope of the tangent at any point \[(x,y)\]on it as\[\frac{{{x}^{2}}-2y}{x},\]then the curve also passes through the point [JEE Main Online Paper Held On 12-Jan-2019 Evening]

    A) \[(-\sqrt{2},1)\]                          

    B) \[(-1,2)\]

    C) \[(\sqrt{3},0)\]               

    D)   \[(3,0)\]

    Correct Answer: C

    Solution :

    Here,\[=\frac{dy}{dx}=\frac{{{x}^{2}}-2y}{x}\]\[\Rightarrow \]\[\frac{dy}{dx}+\frac{2}{x}y=x\] \[\therefore \]\[I.F.={{e}^{\int_{{}}^{{}}{\frac{2}{x}dx}}}={{x}^{2}}\] \[\therefore \]Solutions is\[y.{{x}^{2}}=\int_{{}}^{{}}{x.{{x}^{2}}dx+C}\] \[\Rightarrow \]\[y{{x}^{2}}=\frac{{{x}^{4}}}{4}+C\] Since, the curve passes through the point (\[1,\text{ }-2\]). \[\therefore \]\[-2=\frac{1}{4}+C\Rightarrow C=\frac{-9}{4}\] \[\therefore \]\[y{{x}^{2}}=\frac{{{x}^{4}}}{4}-\frac{9}{4}\]\[\Rightarrow \]\[{{x}^{4}}-4{{x}^{2}}y-9=0\] Now, only the point in option i.e., \[(\sqrt{3},0)\]satisfies the above equation.


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