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Please solve RD Sharma class 12 chapter Determinants exercise multiple choise question 13 maths textbook solution

Answers (1)

Answer:

Correct option (a)

Hint:

Simply solve this determinant.

Given:

        \Delta=\left|\begin{array}{ccc} 1 & \omega^{n} & \omega^{2 n} \\ \omega^{2 n} & 1 & \omega^{n} \\ \omega^{n} & \omega^{2 n} & 1 \end{array}\right|

We have to find \Delta

Solution:

        \Delta=\left|\begin{array}{ccc} 1 & \omega^{n} & \omega^{2 n} \\ \omega^{2 n} & 1 & \omega^{n} \\ \omega^{n} & \omega^{2 n} & 1 \end{array}\right|

Applying C1→C1+C2+C3

        \Rightarrow \Delta=\left|\begin{array}{ccc} 1+\omega^{n}+\omega^{2n} & \omega^{n} & \omega^{2 n} \\ 1+\omega^{n}+\omega^{2n} & 1 & \omega^{n} \\ 1+\omega^{n}+\omega^{2n} & \omega^{2 n} & 1 \end{array}\right|

        \Rightarrow \Delta=\left|\begin{array}{ccc} 0 & \omega^{n} & \omega^{2 n} \\ 0 & 1 & \omega^{n} \\ 0 & \omega^{2 n} & 1 \end{array}\right|                            [\because 1+\omega ^{n}+\omega ^{2n}=0]

        \Rightarrow \Delta=0

Posted by

Gurleen Kaur

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