BCECE Engineering BCECE Engineering Solved Paper-2004

  • question_answer
    The eccentricity of the ellipse\[9{{x}^{2}}+5{{y}^{2}}-30y=0\]is:

    A)  1/3                                       

    B)  2/3

    C)  3/4                       

    D)         none of these

    Correct Answer: B

    Solution :

    Given equation of ellipse is \[9{{x}^{2}}+5{{y}^{2}}-30y=0\] or \[9{{x}^{2}}+5({{y}^{2}}-6y+9)=45\] or            \[\frac{{{x}^{2}}}{5}+\frac{{{(y-3)}^{2}}}{9}=1\] On comparing with\[\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\]                 Here,     \[{{a}^{2}}=5,\,{{b}^{2}}=9\] \[\therefore \] Eccentricity,\[e=\sqrt{1-\frac{{{a}^{2}}}{{{b}^{2}}}}\]       \[(\because \,b>a)\]                                 \[=\sqrt{1-\frac{5}{9}}=\frac{2}{3}\] Note: Eccentricity of ellipse is lying between 0 to 1.


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