CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2008

  • question_answer
    If \[{{e}_{1}}\] and \[{{e}_{2}}\] are the eccentricities of a hyperbola  \[3{{x}^{2}}-3{{y}^{2}}=25\] and its conjugate, then

    A)  \[e_{1}^{2}+e_{2}^{2}=2\]       

    B)  \[e_{1}^{2}+e_{2}^{2}=4\]

    C)  \[{{e}_{1}}+{{e}_{2}}=4\]

    D)  \[{{e}_{1}}+{{e}_{2}}=\sqrt{2}\]   

    Correct Answer: B

    Solution :

    Given equation can be rewritten as \[{{x}^{2}}-{{y}^{2}}=\frac{25}{3}\] Here,          \[{{a}^{2}}=1,{{b}^{2}}=1\] \[\therefore \]  s\[{{e}_{1}}=\sqrt{1+\frac{{{b}^{2}}}{{{a}^{2}}}}=\sqrt{1+1}=\sqrt{2}\] The equation of conjugate hyperbola is                 \[-{{x}^{2}}+{{y}^{2}}=\frac{25}{3}\] \[\therefore \]  \[{{e}_{2}}=\sqrt{1+\frac{{{a}^{2}}}{{{b}^{2}}}}=\sqrt{1+1}=\sqrt{2}\] \[\therefore \]  \[e_{1}^{2}+e_{2}^{2}={{(\sqrt{2})}^{2}}+{{(\sqrt{2})}^{2}}=4\]


You need to login to perform this action.
You will be redirected in 3 sec spinner