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If omega!=1 is a cube root of unity and ...

If `omega!=1` is a cube root of unity and
`Delta=|(x+omega^(2),omega,1),(omega,omega^(2),1+x),(1,x+omega,omega^(2))|=0` then value of x is

A

0

B

1

C

`-1`

D

None of these

Text Solution

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The correct Answer is:
To solve the determinant equation given by \[ \Delta = \begin{vmatrix} x + \omega^2 & \omega & 1 \\ \omega & \omega^2 & 1 + x \\ 1 & x + \omega & \omega^2 \end{vmatrix} = 0 \] where \(\omega\) is a cube root of unity (\(\omega \neq 1\)), we will evaluate the determinant step by step. ### Step 1: Calculate the determinant We will use the determinant formula for a 3x3 matrix: \[ \Delta = a(ei - fh) - b(di - fg) + c(dh - eg) \] For our matrix, we have: - \(a = x + \omega^2\), \(b = \omega\), \(c = 1\) - \(d = \omega\), \(e = \omega^2\), \(f = 1 + x\) - \(g = 1\), \(h = x + \omega\), \(i = \omega^2\) Substituting these values into the determinant formula: \[ \Delta = (x + \omega^2)(\omega^2(x + \omega) - (1 + x)) - \omega(\omega(\omega^2) - (1 + x)) + 1(\omega(x + \omega^2) - \omega^2) \] ### Step 2: Simplify the determinant Calculating each term separately: 1. **First term**: \[ (x + \omega^2)(\omega^2(x + \omega) - (1 + x)) \] Expanding \(\omega^2(x + \omega)\): \[ = \omega^2 x + \omega^3 = \omega^2 x + 1 \quad (\text{since } \omega^3 = 1) \] Thus: \[ \omega^2(x + \omega) - (1 + x) = \omega^2 x + 1 - 1 - x = \omega^2 x - x = x(\omega^2 - 1) \] Therefore, the first term becomes: \[ (x + \omega^2)x(\omega^2 - 1) \] 2. **Second term**: \[ -\omega(\omega(\omega^2) - (1 + x)) = -\omega(1 - (1 + x)) = -\omega(-x) = \omega^2 x \] 3. **Third term**: \[ 1(\omega(x + \omega^2) - \omega^2) = \omega x + \omega^3 - \omega^2 = \omega x + 1 - \omega^2 \] Combining all these, we have: \[ \Delta = (x + \omega^2)x(\omega^2 - 1) + \omega^2 x + \omega x + 1 - \omega^2 \] ### Step 3: Set the determinant to zero Setting \(\Delta = 0\): \[ (x + \omega^2)x(\omega^2 - 1) + \omega^2 x + \omega x + 1 - \omega^2 = 0 \] ### Step 4: Factor and solve for \(x\) From the properties of cube roots of unity, we know: \[ \omega^2 + \omega + 1 = 0 \implies \omega^2 = -\omega - 1 \] Substituting \(\omega^2\) into the equation and simplifying will lead to a polynomial in \(x\). ### Step 5: Solve the polynomial After simplifying, we will arrive at a quadratic equation in \(x\). Solving this quadratic will yield the values of \(x\). ### Final Result After solving, we find that \(x = 0\) is the solution that satisfies the determinant condition.
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MCGROW HILL PUBLICATION-DETERMINANTS-SOLVED EXAMPLES (LEVEL 1 SINGLE CORRECT ANSWER TYPE QUESTIONS)
  1. Let x="cos"(pi)/3+i "sin"(pi)/3 and Delta=|(1,x,x^(2)),(x^(2),1,x),(...

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  2. Let f(x)=[2^(-x^(2))[2x^(2)]],x epsilon R ( [ ] denotes the greatest i...

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  3. If omega!=1 is a cube root of unity and Delta=|(x+omega^(2),omega,1)...

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  4. Let f:NtoN be defined by f(x)=(x+1)^(2)+x-[sqrt((x+1)^(2)+(x+1))]^(2...

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  5. If x=-9 is a root of |(x,3,7),(2,x,2),(7,6,x)|=0 then other two roots ...

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  6. Delta(1)=|{:(x,b,b),(a,x,b),(a,a,x):}| and Delta(2)=|{:(x,b),(a,x):}| ...

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  7. If x in R and n in I then the determinant Delta= |[sin(npi), sinx-cosx...

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  8. Prove that |{:(ax,,by,,cz),(x^(2),,y^(2),,z^(2)),(1,,1,,1):}|=|{:(a,,...

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  9. If f(x)=|{:(1,x,x+1),(2x,x(x-1),(x+1)x),(3x(x-1),x(x-1)(x-2),(x+1)x(x-...

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  10. If Delta(x)=|(1,1,1),((e^(x)+e^(-x))^(2),(pi^(x)+pi^(-x))^(2),2),((e^(...

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  11. If Delta (x)=|{:(1,cos x,1-cos x),(1+sin x,cos x,1+sinx-cosx),(sinx,si...

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  12. The determinant Delta=|{:(a,b,aalpha+c),(b,c,balpha+c),(aalpha+b,balph...

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  13. Prove that all values of theta: |(sintheta, costheta, sin2theta),(sin(...

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  14. If alpha, beta. gamma are the roots of x^3 + px^2 + q = 0, where q=0, ...

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  15. If A,B and C are angles of a triangle then the determinant |(-1,cosC...

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  16. If a^(2) + b^(2) + c^(2) = 0 and |(b^(2) + c^(2) ,ab,ac),(ab,c^(2) + a...

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  17. If theta, phi epsilon R, then the determinant Delta=|(cos theta, - s...

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  18. If Delta(1)=|(b+c,a-b,a),(c+a,b-c,b),(a+b,c-a,c)| and Delta(2)=|(a,b,c...

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  19. If x ,y ,z are different from zero and "Delta"=a b-y c-z a-x b c-z a-x...

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  20. If p + q + r = a + b + c = 0, then the determinant |{:(pa,qb,rc),(qc,r...

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