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 \[\omega \] is the cube root of unity, then \[\left| \begin{matrix}    1 & \omega  & {{\omega }^{2}}  \\    \omega  & {{\omega }^{2}} & 1  \\    {{\omega }^{2}} & 1 & \omega   \\ \end{matrix} \right|\]=   [RPET 1985, 93, 94; MP PET 1990, 2002;  Karnataka CET 1992; 93, 02, 05]

    A) 1

    B) 0

    C) \[\omega \]

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

    Correct Answer: B

    Solution :

    \[\left| \,\begin{matrix}    1 & \omega  & {{\omega }^{2}}  \\    \omega  & {{\omega }^{2}} & 1  \\    {{\omega }^{2}} & 1 & \omega   \\ \end{matrix}\, \right|=\left| \,\begin{matrix}    1+\omega +{{\omega }^{2}} & \omega  & {{\omega }^{2}}  \\    1+\omega +{{\omega }^{2}} & {{\omega }^{2}} & 1  \\    1+\omega +{{\omega }^{2}} & 1 & \omega   \\ \end{matrix}\, \right|\] \[=\,\left| \,\begin{matrix}    0 & \omega  & {{\omega }^{2}}  \\    0 & {{\omega }^{2}} & 1  \\    0 & 1 & \omega   \\ \end{matrix}\, \right|=0\].


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