CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2002

  • question_answer
    If\[\omega =-\frac{1}{2}+\frac{\sqrt{3i}}{2},\]the value of the determinant\[\left| \begin{matrix}    1 & \omega  & {{\omega }^{2}}  \\    \omega  & {{\omega }^{2}} & 1  \\    {{\omega }^{2}} & 1 & \omega   \\ \end{matrix} \right|\]is:

    A)  zero                     

    B)  3

    C)  \[-1\]                                   

    D) \[1\]

    Correct Answer: A

    Solution :

     \[=\left| \begin{matrix}    1 & \omega  & {{\omega }^{2}}  \\    \omega  & {{\omega }^{2}} & 1  \\    {{\omega }^{2}} & 1 & \omega   \\ \end{matrix} \right|{{C}_{1}}={{C}_{1}}+{{C}_{2}}+{{C}_{3}}\] \[=\left| \begin{matrix}    1+\omega +{{\omega }^{2}} & \omega  & {{\omega }^{2}}  \\    1+\omega +{{\omega }^{2}} & {{\omega }^{2}} & 1  \\    1+\omega +{{\omega }^{2}} & 1 & \omega   \\ \end{matrix} \right|\] \[=\left| \begin{matrix}    0 & \omega  & {{\omega }^{2}}  \\    0 & {{\omega }^{2}} & 1  \\    0 & 1 & \omega   \\ \end{matrix} \right|=0\]


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