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If a,b,c are non-zero real number such t...

If `a,b,c` are non-zero real number such that `|(bc,ca,ab),(ca,ab,bc),(ab,bc,ca)|=0,` then

A

`(1)/(a) + (1)/(b) + (1)/(c) = 0`

B

`(1)/(a) - (1)/(b) - (1)/(c) = 0`

C

`(1)/(b) + (1)/(c) - (1)/(a) = 0`

D

`(1)/(b) - (1)/(c) - (1)/(a) = 0`

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To solve the given problem, we need to evaluate the determinant of the matrix formed by the elements \( (bc, ca, ab), (ca, ab, bc), (ab, bc, ca) \) and set it equal to zero. ### Step-by-Step Solution: 1. **Write the Determinant**: We need to compute the determinant: \[ D = \begin{vmatrix} bc & ca & ab \\ ca & ab & bc \\ ab & bc & ca \end{vmatrix} \] 2. **Expand the Determinant**: We can expand this determinant along the first row: \[ D = bc \begin{vmatrix} ab & bc \\ bc & ca \end{vmatrix} - ca \begin{vmatrix} ca & bc \\ ab & ca \end{vmatrix} + ab \begin{vmatrix} ca & ab \\ ab & bc \end{vmatrix} \] 3. **Calculate the 2x2 Determinants**: Now we compute the 2x2 determinants: - For the first determinant: \[ \begin{vmatrix} ab & bc \\ bc & ca \end{vmatrix} = ab \cdot ca - bc \cdot bc = abc - b^2c^2 \] - For the second determinant: \[ \begin{vmatrix} ca & bc \\ ab & ca \end{vmatrix} = ca \cdot ca - bc \cdot ab = c^2a^2 - abc \] - For the third determinant: \[ \begin{vmatrix} ca & ab \\ ab & bc \end{vmatrix} = ca \cdot bc - ab \cdot ab = cabc - a^2b^2 \] 4. **Substituting Back**: Substitute these back into the determinant: \[ D = bc(abc - b^2c^2) - ca(c^2a^2 - abc) + ab(cabc - a^2b^2) \] 5. **Simplifying**: Expanding this gives: \[ D = b^2c^2a - b^3c^3 - c^2a^3 + abc^2 + abc^2 - a^2b^2c \] Collecting like terms, we can rewrite: \[ D = a^3b + b^3c + c^3a - 3abc(a + b + c) \] 6. **Setting the Determinant to Zero**: Since we know that \( D = 0 \), we have: \[ a^3b + b^3c + c^3a - 3abc(a + b + c) = 0 \] 7. **Using the Identity**: We can use the identity: \[ a^3 + b^3 + c^3 - 3abc = (a + b + c)(a^2 + b^2 + c^2 - ab - ac - bc) \] This implies that either \( a + b + c = 0 \) or \( a^2 + b^2 + c^2 - ab - ac - bc = 0 \). 8. **Conclusion**: If \( a + b + c = 0 \), then: \[ \frac{1}{a} + \frac{1}{b} + \frac{1}{c} = 0 \] Hence, the final result is: \[ \frac{1}{a} + \frac{1}{b} + \frac{1}{c} = 0 \]
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OBJECTIVE RD SHARMA ENGLISH-DETERMINANTS-Exercise
  1. The equation |(x-a,x-b,x-c),(x-b,x-a,x-c),(x-c,x-b,x-a)|=0 (a,b,c are ...

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  2. Let A = [(1,sin theta,1),(- sin theta,1,sin theta),(-1,-sin theta,1)],...

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  3. If a,b,c are non-zero real number such that |(bc,ca,ab),(ca,ab,bc),(ab...

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  4. The value of the determinant |{:(ka,,k^(2)+a^(2),,1),(kb,,k^(2)+b^(2)...

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  5. The system of simulataneous equations kx + 2y -z = 1 (k -1) y -2z ...

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  6. The value of the determinant |(1,omega^(3),omega^(5)),(omega^(3),1,ome...

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  7. If a,b,c are non-zero real number such that |(bc,ca,ab),(ca,ab,bc),(ab...

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  8. If the system of equations x + ay + az = 0 bx + y + bz = 0 cx + ...

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  9. The determinant D=|{:(cos(alpha+beta),-sin(alpha+beta),cos2beta),(sina...

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  10. If omega is a cube root of unity, then Root of polynomial is |(x + 1...

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

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  12. If y= sin px and y(n) is the nth derivative of y, then |{:(y,y(1),y(...

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  13. If |p b c a q c a b r|=0 , find the value of p/(p-a)+q/(q-b)+r/(r-c),\...

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  14. Using properties of determinants, show that |{:(x, p, q), ( p, x, q)...

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  15. The factors of |(x,a,b),(a,x,b),(a,b,x)|, are

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  16. Let omega=-1/2+i(sqrt(3))/2dot Then the value of the determinant |1 1 ...

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  17. If a+b+c=0, one root of |a-x c b c b-x a b a c-x|=0 is x=1 b. x=2 c. ...

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  18. suppose D= |{:(a(1),,b(1),,c(1)),(a(2),,b(2),,c(2)),(a(3),,b(3),,c(3...

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  19. A and B are two non-zero square matrices such that AB = O. Then,

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  20. The roots of the equation |{:(x-1,1,1),(1,x-1,1),(1,1,x-1):}|=0 are

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