CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2005

  • question_answer
    The equation to die hyperbola having its eccentricity 2 and the distance between its foci is 8, is :

    A)  \[\frac{{{x}^{2}}}{12}-\frac{{{y}^{2}}}{4}=1\]                      

    B)  \[\frac{{{x}^{2}}}{4}-\frac{{{y}^{2}}}{12}=1\]

    C)                  \[\frac{{{x}^{2}}}{8}-\frac{{{y}^{2}}}{2}=1\]                        

    D)                  \[\frac{{{x}^{2}}}{16}-\frac{{{y}^{2}}}{9}=1\]

    Correct Answer: B

    Solution :

    Let the equation of hyperbola is                 \[\frac{{{x}^{2}}}{{{a}^{2}}}-\frac{{{y}^{2}}}{{{b}^{2}}}=1\] Given, \[e=2,\text{ }2ne=8\] \[\Rightarrow \]               \[ae=4\Rightarrow a=2\] Now. \[{{b}^{2}}={{a}^{2}}\,({{e}^{2}}-1)\] \[\Rightarrow \]               \[{{b}^{2}}=4\,(4-1)\,\,\Rightarrow \,\,{{b}^{2}}=12\] \[\therefore \] equation of hyperbola is                 \[\frac{{{x}^{2}}}{4}-\frac{{{y}^{2}}}{12}=1\]


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