JEE Main & Advanced JEE Main Paper (Held On 09-Jan-2019 Evening)

  • question_answer
    A hyperbola has its centre at the origin, passes through the point \[\left( 4,\text{ }2 \right)\] and has transverse axis of length 4 along the x-axis. Then the eccentricity of the hyperbola is: [JEE Main Online Paper (Held On 09-Jan-2019 Evening]

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

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

    C)               2                                             

    D)               \[\sqrt{3}\]

    Correct Answer: B

    Solution :

    Let the equation of hyperbola \[\frac{{{x}^{2}}}{{{a}^{2}}}\,-\,\frac{{{y}^{2}}}{{{b}^{2}}}\,=\,1\] Given \[2a=4\] \[\Rightarrow \,\,\,a=2\] It passes through \[\left( 4,\text{ }2 \right)\] \[\therefore \,\,\,\,\frac{16}{4}\,-\,\frac{4}{{{b}^{2}}}\,\,\,=1\,\,\,\Rightarrow \,\,{{b}^{2}}\,=\,\frac{4}{3}\] \[e\,\,=\,\,\sqrt{1+\frac{{{b}^{2}}}{{{a}^{2}}}}\,\,=\,\,\sqrt{1+\frac{4/3}{4}}\] \[=\,\,\sqrt{1+\frac{1}{3}}\,\,=\,\,\frac{2}{\sqrt{3}}\]   


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