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if w is a complex cube root to unity...

if w is a complex cube root to unity then value of
` Delta =|{:(a_(1)+b_(1)w,,a_(1)w^(2)+b_(1),,c_(1)+b_(1)bar(w)),(a_(2)+b_(2)w,,a_(2)w^(2)+b_(2),,c_(2)+b_(2)bar(w)),(a_(3)+b_(3)w,,a_(3)w^(2)+b_(3),,c_(3)+b_(3)bar(w)):}|` is

A

0

B

-1

C

2

D

none of these

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The correct Answer is:
To solve the given problem, we need to evaluate the determinant: \[ \Delta = \begin{vmatrix} a_1 + b_1 \omega & a_1 \omega^2 + b_1 & c_1 + b_1 \bar{\omega} \\ a_2 + b_2 \omega & a_2 \omega^2 + b_2 & c_2 + b_2 \bar{\omega} \\ a_3 + b_3 \omega & a_3 \omega^2 + b_3 & c_3 + b_3 \bar{\omega} \end{vmatrix} \] where \(\omega\) is a complex cube root of unity. ### Step 1: Understanding the properties of cube roots of unity The complex cube roots of unity are \(1, \omega, \omega^2\), where: - \(\omega = e^{2\pi i / 3} = -\frac{1}{2} + \frac{\sqrt{3}}{2} i\) - \(\omega^2 = e^{-2\pi i / 3} = -\frac{1}{2} - \frac{\sqrt{3}}{2} i\) - The important property is that \(\omega^3 = 1\) and \(1 + \omega + \omega^2 = 0\). ### Step 2: Multiply the second column by \(\omega\) We can multiply the second column of the determinant by \(\omega\). According to the properties of determinants, multiplying a column by a scalar multiplies the determinant by that scalar. \[ \Delta = \frac{1}{\omega} \begin{vmatrix} a_1 + b_1 \omega & a_1 \omega^3 + b_1 \omega & c_1 + b_1 \bar{\omega} \\ a_2 + b_2 \omega & a_2 \omega^3 + b_2 \omega & c_2 + b_2 \bar{\omega} \\ a_3 + b_3 \omega & a_3 \omega^3 + b_3 \omega & c_3 + b_3 \bar{\omega} \end{vmatrix} \] Since \(\omega^3 = 1\), we can simplify the determinant: \[ \Delta = \frac{1}{\omega} \begin{vmatrix} a_1 + b_1 \omega & a_1 + b_1 \omega & c_1 + b_1 \bar{\omega} \\ a_2 + b_2 \omega & a_2 + b_2 \omega & c_2 + b_2 \bar{\omega} \\ a_3 + b_3 \omega & a_3 + b_3 \omega & c_3 + b_3 \bar{\omega} \end{vmatrix} \] ### Step 3: Identifying identical columns Now we can see that the first and second columns are identical: \[ \begin{vmatrix} x & x & z \\ y & y & w \\ z & z & v \end{vmatrix} \] where \(x = a_i + b_i \omega\), \(y = a_i + b_i \omega\), and \(z = c_i + b_i \bar{\omega}\). ### Step 4: Conclusion The determinant of a matrix with two identical columns is zero. Therefore, we conclude: \[ \Delta = 0 \] ### Final Answer The value of the determinant \(\Delta\) is \(0\). ---

To solve the given problem, we need to evaluate the determinant: \[ \Delta = \begin{vmatrix} a_1 + b_1 \omega & a_1 \omega^2 + b_1 & c_1 + b_1 \bar{\omega} \\ a_2 + b_2 \omega & a_2 \omega^2 + b_2 & c_2 + b_2 \bar{\omega} \\ a_3 + b_3 \omega & a_3 \omega^2 + b_3 & c_3 + b_3 \bar{\omega} \end{vmatrix} ...
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Knowledge Check

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