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If omega is a complex cube root of unity...

If `omega` is a complex cube root of unity, then value of
`Delta=|(a_(1)+b_(1)omega, a_(1)omega^(2)+b_(1),c_(1)+b_(1)omega),(a_(2)+b_(2)omega,a_(2)omega^(2)+b_(2),c_(2)+b_(2)omega),(a_(3)+b_(3)omega,a_(3)omega^(2)+b_(3),c_(3)+b_(3)omega)|` is

A

0

B

`-1`

C

2

D

None of these

Text Solution

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The correct Answer is:
To find the value of the determinant \( \Delta \) given by \[ \Delta = \begin{vmatrix} a_1 + b_1 \omega & a_1 \omega^2 + b_1 & c_1 + b_1 \omega \\ a_2 + b_2 \omega & a_2 \omega^2 + b_2 & c_2 + b_2 \omega \\ a_3 + b_3 \omega & a_3 \omega^2 + b_3 & c_3 + b_3 \omega \end{vmatrix} \] where \( \omega \) is a complex cube root of unity, we can proceed with the following steps: ### Step 1: Understand the properties of \( \omega \) Recall that \( \omega \) satisfies the equations: 1. \( 1 + \omega + \omega^2 = 0 \) 2. \( \omega^3 = 1 \) ### Step 2: Manipulate the second column We will multiply the second column by \( \omega \): \[ \text{Column 2} = \omega \cdot (a_1 \omega^2 + b_1, a_2 \omega^2 + b_2, a_3 \omega^2 + b_3) \] This gives us: \[ \Delta = \begin{vmatrix} a_1 + b_1 \omega & \omega(a_1 \omega^2 + b_1) & c_1 + b_1 \omega \\ a_2 + b_2 \omega & \omega(a_2 \omega^2 + b_2) & c_2 + b_2 \omega \\ a_3 + b_3 \omega & \omega(a_3 \omega^2 + b_3) & c_3 + b_3 \omega \end{vmatrix} \] ### Step 3: Simplify the second column Since \( \omega^3 = 1 \), we can simplify: \[ \omega(a_i \omega^2 + b_i) = a_i + b_i \omega \] Thus, the determinant becomes: \[ \Delta = \begin{vmatrix} a_1 + b_1 \omega & a_1 + b_1 \omega & c_1 + b_1 \omega \\ a_2 + b_2 \omega & a_2 + b_2 \omega & c_2 + b_2 \omega \\ a_3 + b_3 \omega & a_3 + b_3 \omega & c_3 + b_3 \omega \end{vmatrix} \] ### Step 4: Identify proportional columns Now we see that the first and second columns are identical: \[ \text{Column 1} = \text{Column 2} \] This means that the columns of the determinant are linearly dependent. ### Step 5: Conclude the value of the determinant Since the determinant has two identical columns, we conclude that: \[ \Delta = 0 \] Thus, the value of the determinant \( \Delta \) is \( \boxed{0} \). ---
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If omega is a non-real cube root of unity, then Delta = |(a_(1) + b_(1) omega,a_(1) omega^(2) + b_(1),a_(1) + b_(1) + c_(1) omega^(2)),(a_(2) + b_(2) omega,a_(2) omega^(2) + b_(2),a_(2) + b_(2) omega + c_(2) omega^(2)),(a_(3) + b_(3) omega,a_(3) omega^(2) + b_(3),a_(3) + b_(3) omega + c_(3) omega^(2))| is equal to

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det[[2a_(1)b_(1),a_(1)b_(2)+a_(2)b_(1),a_(1)b_(3)+a_(3)b_(1)a_(1)b_(2)+a_(2)b_(1),2a_(2)b_(2),a_(2)b_(3)+a_(3)b_(2)a_(1)b_(3)+a_(3)b_(1),a_(3)b_(2)+a_(2)b_(3),2a_(3)b_(3)]]=

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