JEE Main & Advanced Mathematics Complex Numbers and Quadratic Equations Question Bank Self Evaluation Test - Complex Numbers and Quadratic Equations

  • question_answer
    If both the roots of the equation \[{{x}^{2}}-2kx+{{k}^{2}}-4=0\] lie between \[-3\] and 5, then which one of the following is correct?

    A) \[-2<k<2\]    

    B) \[-5<k<3\]

    C) \[-3<k<5\]    

    D) \[-1<k<3\]

    Correct Answer: D

    Solution :

    \[{{\operatorname{x}}^{2}}-2kx+{{k}^{2}}-4=0\] \[\Rightarrow \,\,\,{{(x-k)}^{2}}-{{2}^{2}}=0\] \[\Rightarrow \,\,\,\left( x-k\,-\,2 \right)\left( x-k+2 \right)=0\] \[\Rightarrow \,\,\,\,x=k+2,\,\,k-2\] \[\Rightarrow \,\,\,\operatorname{k}+2<5\,\,\,\And \,\,k-2>-\,3\] \[\Rightarrow \,\,\,\,\operatorname{k}<3\,\,\,\And \,\,\,k>-1\] \[\Rightarrow \,\,\,\,-1<k<3\]


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