J & K CET Engineering J and K - CET Engineering Solved Paper-2005

  • question_answer
    If one of the roots of equation \[{{x}^{2}}+ax+3=0\] is 3 and one of the roots of the equation \[{{x}^{2}}+ax+b=0\]is three times the other root, then the value of b is equal to

    A)  \[3\]           

    B)  \[4\]

    C)  \[2\]             

    D)  \[1\]

    Correct Answer: A

    Solution :

    Let \[\alpha \] and 3 are the roots of the equation \[{{x}^{2}}+ax+3=0\]. \[\therefore \] \[3a=3\,\,\,\,\,\Rightarrow \,\,\,\,\,\,\,\alpha =1\] and \[3+\alpha =-a\] \[\Rightarrow \] \[-a=4\,\,\,\,\Rightarrow \,\,\,\,a=-4\] Again, let \[\beta \] and \[3\beta \] are the roots of the equation \[{{x}^{2}}+ax+b=0\] \[\therefore \] \[\beta +3\beta =-a\] \[\Rightarrow \] \[4\beta =4\,\,\,\Rightarrow \,\,\,\,\beta =1\] and \[\beta .3\beta =b\,\,\,\Rightarrow \,\,\,b=3\]


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