JEE Main & Advanced Mathematics Conic Sections Question Bank Hyperbola

  • question_answer
    The eccentricity of the hyperbola conjugate to \[{{x}^{2}}-3{{y}^{2}}=2x+8\] is [UPSEAT 2004]

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

    B)            \[\sqrt{3}\]

    C)            2     

    D)            None of these

    Correct Answer: C

    Solution :

                      Given, equation of hyperbola is \[{{x}^{2}}-3{{y}^{2}}=2x+8\]                   Þ \[{{x}^{2}}-2x-3{{y}^{2}}=8\]                   Þ \[{{(x-1)}^{2}}-3{{y}^{2}}=9\] Þ \[\frac{{{(x-1)}^{2}}}{9}-\frac{{{y}^{2}}}{3}=1\]                   Conjugate of this hyperbola is \[-\frac{{{(x-1)}^{2}}}{9}+\frac{{{y}^{2}}}{3}=1\]                   and its eccentricity \[(e)=\sqrt{\left( \frac{{{a}^{2}}+{{b}^{2}}}{{{b}^{2}}} \right)}\]                    Here, \[{{a}^{2}}=9\], \[{{b}^{2}}=3\]; \[\therefore \] \[e=\sqrt{\frac{9+3}{3}}=2\].


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