JEE Main & Advanced JEE Main Paper (Held On 9 April 2017)

  • question_answer
    The eccentricity of an ellipse having centre at the origin, axes along the co-ordinate axes and passing through the points (4, -1) and (-2, 2) is :                          [JEE Online 09-04-2017]

    A)  \[\frac{\sqrt{3}}{2}\]                                    

    B)  \[\frac{\sqrt{3}}{4}\]

    C)  \[\frac{2}{\sqrt{5}}\]                                    

    D)  \[\frac{1}{2}\]

    Correct Answer: A

    Solution :

                                    \[e=?,\] centre at (0, 0)                 \[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\] \[\frac{16}{{{a}^{2}}}+\frac{1}{{{b}^{2}}}=1\] \[16{{b}^{2}}+{{a}^{2}}={{a}^{2}}{{b}^{2}}\]                                         ?(1) \[\frac{4}{{{a}^{2}}}+\frac{4}{{{b}^{2}}}=1\] \[4{{b}^{2}}+4{{a}^{2}}={{a}^{2}}{{b}^{2}}\]                                         ?(2) From (1) & (2) \[16{{b}^{2}}+{{a}^{2}}=4{{a}^{2}}+4{{b}^{2}}\] \[3{{a}^{2}}=12{{b}^{2}}\,=\]


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