JEE Main & Advanced Mathematics Determinants & Matrices Question Bank Expansion of determinants, Solution of equation in the form of determinants and properties of determinants

  • question_answer
    If \[\omega \] be a complex cube root of unity, then                           \[\left| \,\begin{matrix}    1 & \omega  & -{{\omega }^{2}}/2  \\    1 & 1 & 1  \\    1 & -1 & 0  \\ \end{matrix}\, \right|=\]

    A) 0

    B) 1

    C) \[\omega \]

    D) \[{{\omega }^{2}}\]

    Correct Answer: A

    Solution :

    \[\left| \,\begin{matrix}    1 & \omega  & -{{\omega }^{2}}/2  \\    1 & 1 & 1  \\    1 & -1 & 0  \\ \end{matrix}\, \right|=-\frac{1}{2}\left| \,\begin{matrix}    1 & \omega  & {{\omega }^{2}}  \\    1 & 1 & -2  \\    1 & -1 & 0  \\ \end{matrix}\, \right|\] = \[-\frac{1}{2}\left| \,\begin{matrix}    0 & \omega  & {{\omega }^{2}}  \\    0 & 1 & -2  \\    0 & -1 & 0  \\ \end{matrix}\, \right|=0\],(Apply \[{{C}_{1}}\to {{C}_{1}}+{{C}_{2}}+{{C}_{3}})\].


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