CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2006

  • question_answer
    If a, b and c are in geometric progression and the roots of the equations\[a{{x}^{2}}+2bx+c=0\]are \[\alpha \] and \[\beta \] and those of\[e{{x}^{2}}+2\text{ }bx+a=0\]are \[\gamma \] and \[\delta ,\] then:

    A)  \[\alpha \ne \beta \ne \gamma \ne \delta \]    

    B)  \[\alpha \ne \beta and\,\gamma \ne \delta \]

    C)  \[a\alpha =a\beta =c\gamma =c\delta \]            

    D)  \[\alpha =\beta \,and\,\gamma \ne \delta \]

    E)  \[\alpha \ne \beta \,and\,\gamma =\delta \]

    Correct Answer: B

    Solution :

    Since\[\alpha \]and\[\beta \]are the roots of the equation\[a{{x}^{2}}+2bx+c=0\] \[\Rightarrow \]\[\alpha +\beta =-\frac{b}{a},\alpha \beta =\frac{c}{a}\] And\[\gamma ,\delta \]are the roots of the equation \[c{{x}^{2}}+2bx+a=0\] \[\Rightarrow \]     \[\gamma +\delta =\frac{-b}{c}\]and \[\delta \gamma =\frac{a}{c}\] Since, a, b, c are in GP\[\Rightarrow \]\[{{b}^{2}}=ac\] Now, if\[\alpha =\beta \Rightarrow {{b}^{2}}=4ac\therefore \alpha \ne \beta \] and if\[\gamma =\delta \Rightarrow {{b}^{2}}=4ac\therefore \gamma \ne \delta \]


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