JEE Main & Advanced Mathematics Conic Sections Question Bank Ellipse

  • question_answer
    The equation of the ellipse whose one focus is at (4, 0) and whose eccentricity is 4/5, is                 [Karnataka CET 1993]

    A)            \[\frac{{{x}^{2}}}{{{3}^{2}}}+\frac{{{y}^{2}}}{{{5}^{2}}}=1\]        

    B)            \[\frac{{{x}^{2}}}{{{5}^{2}}}+\frac{{{y}^{2}}}{{{3}^{2}}}=1\]

    C)            \[\frac{{{x}^{2}}}{{{5}^{2}}}+\frac{{{y}^{2}}}{{{4}^{2}}}=1\]        

    D)            \[\frac{{{x}^{2}}}{{{4}^{2}}}+\frac{{{y}^{2}}}{{{5}^{2}}}=1\]

    Correct Answer: B

    Solution :

               Here \[ae=4\]and\[e=\frac{4}{5}\Rightarrow a=5\]            Now \[{{b}^{2}}={{a}^{2}}(1-{{e}^{2}})\Rightarrow {{b}^{2}}=25\left( 1-\frac{16}{25} \right)=9\]            Hence equation of the ellipse is \[\frac{{{x}^{2}}}{25}+\frac{{{y}^{2}}}{9}=1\].


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