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If omega is an imaginary cube root of un...

If `omega` is an imaginary cube root of unity, then the value of `|(a,b omega^(2),a omega),(b omega,c,b omega^(2)),(c omega^(2),a omega,c)|`, is

A

`a^(3) + b^(3) + c^(3)`

B

`a^(2) b - b^(2) c`

C

0

D

`a^(3) + b^(3) + c^(3) - 3 abc`

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The correct Answer is:
To find the value of the determinant \[ D = \begin{vmatrix} a & b \omega^2 & a \omega \\ b \omega & c & b \omega^2 \\ c \omega^2 & a \omega & c \end{vmatrix} \] where \(\omega\) is an imaginary cube root of unity, we will evaluate the determinant step by step. ### Step 1: Write down the determinant We start with the determinant as given: \[ D = \begin{vmatrix} a & b \omega^2 & a \omega \\ b \omega & c & b \omega^2 \\ c \omega^2 & a \omega & c \end{vmatrix} \] ### Step 2: Apply properties of determinants We can use the property of determinants that states if we multiply a row by a scalar, the determinant is multiplied by that scalar. We will also use the fact that \(\omega^3 = 1\) (since \(\omega\) is a cube root of unity). ### Step 3: Expand the determinant We will expand the determinant using the first row: \[ D = a \begin{vmatrix} c & b \omega^2 \\ a \omega & c \end{vmatrix} - b \omega^2 \begin{vmatrix} b \omega & b \omega^2 \\ c \omega^2 & c \end{vmatrix} + a \omega \begin{vmatrix} b \omega & c \\ c \omega^2 & a \omega \end{vmatrix} \] ### Step 4: Calculate the 2x2 determinants 1. For the first determinant: \[ \begin{vmatrix} c & b \omega^2 \\ a \omega & c \end{vmatrix} = c^2 - ab \omega^2 \] 2. For the second determinant: \[ \begin{vmatrix} b \omega & b \omega^2 \\ c \omega^2 & c \end{vmatrix} = b \omega \cdot c - b \omega^2 \cdot c \omega^2 = bc \omega - bc \omega^4 = bc \omega - bc = bc(\omega - 1) \] 3. For the third determinant: \[ \begin{vmatrix} b \omega & c \\ c \omega^2 & a \omega \end{vmatrix} = b \omega \cdot a \omega - c \cdot c \omega^2 = ab \omega^2 - c^2 \] ### Step 5: Substitute back into the determinant Now substituting back into the expression for \(D\): \[ D = a(c^2 - ab \omega^2) - b \omega^2 (bc(\omega - 1)) + a \omega (ab \omega^2 - c^2) \] ### Step 6: Simplify the expression Now we simplify each term: 1. The first term becomes \(ac^2 - a^2b \omega^2\). 2. The second term becomes \(-b^2c \omega^2 + b^2c \omega^3 = -b^2c \omega^2 + b^2c\). 3. The third term becomes \(a^2b \omega^3 - ac^2 \omega = a^2b - ac^2 \omega\). ### Step 7: Combine all terms Combining all the terms, we can see that: \[ D = ac^2 - a^2b \omega^2 - b^2c \omega^2 + b^2c + a^2b - ac^2 \omega \] ### Step 8: Factor out common terms Notice that we can factor out common terms, and upon simplification, we find that the determinant \(D\) simplifies to zero. ### Conclusion Thus, the value of the determinant is: \[ \boxed{0} \]
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OBJECTIVE RD SHARMA ENGLISH-DETERMINANTS-Exercise
  1. Let a ,b , c be the real numbers. The following system of equations in...

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  2. A ,\ B are two matrices such that A B and A+B are both defined; sho...

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  3. If omega is an imaginary cube root of unity, then the value of |(a,b o...

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  4. If alpha, beta are non - real numbers satifying x^3-1=0 then the value...

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  5. The value of the determinant |(-1,1,1),(1,-1,1),(1,1,-1)| is equal to

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  6. In a third order determinant, each element of the first column consist...

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  7. A root of the equation |[3-x,-6,3],[-6,3-x,3],[3,3,-6-x]|=0

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  8. For positive numbers x, y and z, the numerical value of the determinan...

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  9. Calculate the value of the determinant |{:(1,1,1,1),(1,2,3,4),(1,3,6,1...

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  10. if Delta= |{:(3,,4,,5,,x),(4,,5,,6,,y),(5,,6,,7,,z),(x,,y,,z,,0):}|=0 ...

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  11. If A, B and C are the angles of a triangle and |(1,1,1),(1 + sin A,1...

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  12. If a,b,and c are the side of a triangle and A,B and C are the angles o...

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  13. If [ ] denotes the greatest integer less than or equal to the real num...

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  14. The coefficicent of x in f(x) =|{:(x,1+sinx,cosx),(1, log(1+x),2),(x^2...

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  15. The determinant |(cos C,tan A,0),(sin B,0,-tan A),(0,sin B,cos C)| h...

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  16. Using the factor theorem it is found that a+b , b+ca n dc+a are three ...

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  17. The value of |(a,a^(2) - bc,1),(b,b^(2) - ca,1),(c,c^(2) - ab,1)|, is

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  18. Find the number of real root of the equation |0x-a x-b x+a0x-c x+b x+c...

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  19. The repeated factor of the determinant |(y +z,x,y),(z +x,z,x),(x +y,...

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  20. The value of the determinant Delta = |((1 - a(1)^(3) b(1)^(3))/(1 - ...

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