J & K CET Engineering J and K - CET Engineering Solved Paper-2004

  • question_answer
    If the roots of the equation \[3{{x}^{2}}-6x+5=0\] are \[\alpha \] and \[\beta ,\] then the equation whose roots are \[\alpha +\beta \]and\[\frac{2}{\alpha +\beta }\]will be

    A)  \[{{x}^{2}}+3x-1=0\]

    B)  \[{{x}^{2}}+3x-2=0\]

    C)  \[{{x}^{2}}+3x+2=0\]

    D)  \[{{x}^{2}}-3x+2=0\]

    Correct Answer: D

    Solution :

    Given equation is \[3{{x}^{2}}-6x+5=0\] \[\therefore \]   \[\alpha +\beta =2\] and \[\alpha \,\,\beta =\frac{5}{3}\] Now,    \[\alpha +\beta +\frac{2}{\alpha +\beta }=2+\frac{2}{2}=3\] and \[(\alpha +\beta )\times \frac{2}{\alpha +\beta }=2\] \[\therefore \]   Required equation is \[{{x}^{2}}-\left( (\alpha +\beta )+\frac{2}{\alpha +\beta } \right)x+\left( (\alpha +\beta )\times \frac{2}{\alpha +\beta } \right)=0\] \[\Rightarrow \] \[{{x}^{2}}-3x+2=0\]


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