2. Solved Papers
  3. JEE Main & Advanced

JEE Main & Advanced JEE Main Paper (Held on 12-4-2019 Morning)

  • question_answer
    If\[B=\left[ \begin{matrix}    5 & 2\alpha  & 1  \\    0 & 2 & 1  \\    \alpha  & 3 & -1  \\ \end{matrix} \right]\]is the inverse of a \[3\times 3\]matrix A, then the sum of all values of\[\alpha \]for which det + 1 = 0, is :                                                                [JEE Main Held on 12-4-2019 Morning]

    A) 0                                 

    B) 2

    C) 1         

    D) -1

    Correct Answer: C

    Solution :

    \[|B|=5(-5)-2\alpha (-\alpha )-2\alpha \]           \[=2{{\alpha }^{2}}-2\alpha -25\]           \[1+A|=0\]           \[{{\alpha }^{2}}-\alpha -12=0\]             Sum = 1                     


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