JEE Main & Advanced Mathematics Conic Sections Question Bank Ellipse

  • question_answer
    The locus of a variable point whose distance from (?2, 0) is \[\frac{2}{3}\] times its distance from the line \[x=-\frac{9}{2}\], is                 [IIT 1994]

    A)            Ellipse                                       

    B)            Parabola

    C)            Hyperbola                                 

    D)            None of these

    Correct Answer: A

    Solution :

               Let point P \[({{x}_{1}},{{y}_{1}})\]            So,\[\sqrt{{{({{x}_{1}}+2)}^{2}}+y_{1}^{2}}=\frac{2}{3}\left( {{x}_{1}}+\frac{9}{2} \right)\]                    Þ \[{{({{x}_{1}}+2)}^{2}}+y_{1}^{2}=\frac{4}{9}{{\left( {{x}_{1}}+\frac{9}{2} \right)}^{2}}\]                    Þ \[9[x_{1}^{2}+y_{1}^{2}+4{{x}_{1}}+4]=4\left( x_{1}^{2}+\frac{81}{4}+9{{x}_{1}} \right)\]                    Þ \[5x_{1}^{2}+9y_{1}^{2}=45\]Þ\[\frac{x_{1}^{2}}{9}+\frac{y_{1}^{2}}{5}=1\],                    Locus of \[({{x}_{1}},\,{{y}_{1}})\] is\[\frac{{{x}^{2}}}{9}+\frac{{{y}^{2}}}{5}=1\], which is equation of an ellipse.


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