JEE Main & Advanced Mathematics Conic Sections Question Bank Ellipse

  • question_answer
    An ellipse passes through the point (?3, 1) and its eccentricity is \[\sqrt{\frac{2}{5}}\]. The equation of the ellipse is

    A)            \[3{{x}^{2}}+5{{y}^{2}}=32\]     

    B)            \[3{{x}^{2}}+5{{y}^{2}}=25\]

    C)            \[3{{x}^{2}}+{{y}^{2}}=4\]         

    D)            \[3{{x}^{2}}+{{y}^{2}}=9\]

    Correct Answer: A

    Solution :

               Let the equation of ellipse be \[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\]                    \[\because \] It passes through (? 3, 1)                    So \[\frac{9}{{{a}^{2}}}+\frac{1}{{{b}^{2}}}=1\Rightarrow 9+\frac{{{a}^{2}}}{{{b}^{2}}}={{a}^{2}}\]                     .....(i)                    Given eccentricity is \[\sqrt{2/5}\]                    So \[\frac{2}{5}=1-\frac{{{b}^{2}}}{{{a}^{2}}}\Rightarrow \frac{{{b}^{2}}}{{{a}^{2}}}=\frac{3}{5}\]                                       .....(ii)                    From equation (i) and (ii), \[{{a}^{2}}=\frac{32}{3},{{b}^{2}}=\frac{32}{5}\]                    Hence required equation of ellipse is \[3{{x}^{2}}+5{{y}^{2}}=32\].


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