J & K CET Engineering J and K - CET Engineering Solved Paper-2007

  • question_answer
    If the difference between the roots of \[{{x}^{2}}+ax-b=0\]is equal to the difference between the roots of \[{{x}^{2}}-px+q=0,\]then \[{{a}^{2}}-{{p}^{2}}\]in terms of b and q is

    A)  \[-4(b+q)\]     

    B)   \[4(b+q)\]

    C)  \[4(b-q)\]       

    D)  \[4(q-b)\]

    Correct Answer: A

    Solution :

    Let \[\alpha ,\beta \] are the roots of the equation \[{{x}^{2}}+ax-b=0\] \[\therefore \] \[\alpha +\beta =-a,\,\,\alpha \beta =-b\] and \[\gamma ,\delta \] are the roots of the equation \[{{x}^{2}}-px+q=0\] \[\therefore \] \[\gamma +\delta =p,\,\gamma \delta =q\] Given, \[\alpha -\beta =\gamma -\delta \] \[\Rightarrow \] \[{{(\alpha -\beta )}^{2}}={{(\gamma -\delta )}^{2}}\] \[\Rightarrow \] \[{{(\alpha +\beta )}^{2}}-4\alpha \beta ={{(\gamma +\delta )}^{2}}-4\gamma \delta \] \[\Rightarrow \] \[{{a}^{2}}+4b={{p}^{2}}-4q\] \[\Rightarrow \] \[{{a}^{2}}-{{p}^{2}}=-4(b+q)\]


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