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If A = [[a,b,c],[x,y,z],[p,q,r]], B= [[q...

If `A = [[a,b,c],[x,y,z],[p,q,r]], B= [[q , -b,y],[-p,a,-x],[r,-c,z]]` and if A is
invertible, then which of the following is not true?

A

`abs(A) = abs(B)`

B

`abs(A) = -abs(B)`

C

`abs(adjA) = abs(adjB)`

D

A is invertible `hArr` B is invertble

Text Solution

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The correct Answer is:
To solve the problem, we need to analyze the matrices \( A \) and \( B \) given in the question and understand the implications of the invertibility of matrix \( A \). ### Step-by-Step Solution: 1. **Define the Matrices**: \[ A = \begin{bmatrix} a & b & c \\ x & y & z \\ p & q & r \end{bmatrix}, \quad B = \begin{bmatrix} q & -b & y \\ -p & a & -x \\ r & -c & z \end{bmatrix} \] 2. **Understanding Invertibility**: Since \( A \) is given to be invertible, this implies that the determinant of \( A \) is non-zero: \[ \text{det}(A) \neq 0 \] 3. **Calculate the Determinant of Matrix \( B \)**: We can express the determinant of \( B \) in terms of the determinant of \( A \). To do this, we can perform row and column operations on \( B \) to relate it to \( A \). 4. **Row Operations**: - Take \(-1\) common from the second row of \( B \): \[ \text{det}(B) = -\text{det}\begin{bmatrix} q & -b & y \\ p & -a & x \\ r & -c & z \end{bmatrix} \] 5. **Column Operations**: - Take \(-1\) common from the second column of \( B \): \[ \text{det}(B) = (-1)(-1)\text{det}\begin{bmatrix} q & b & y \\ p & a & x \\ r & c & z \end{bmatrix} = \text{det}\begin{bmatrix} q & b & y \\ p & a & x \\ r & c & z \end{bmatrix} \] 6. **Relate \( B \) to \( A \)**: By rearranging the columns and rows, we can show that: \[ \text{det}(B) = -\text{det}(A) \] 7. **Conclusion on Invertibility**: Since \( \text{det}(A) \neq 0 \), it follows that \( \text{det}(B) \neq 0 \) as well. Therefore, both matrices \( A \) and \( B \) are invertible. 8. **Evaluate the Statements**: We need to determine which of the following statements is not true: - \( \text{det}(A) = \text{det}(B) \) - \( \text{det}(A) = -\text{det}(B) \) - \( \text{adj}(A) = \text{adj}(B) \) - If \( A \) is invertible, then \( B \) is invertible. - If \( B \) is invertible, then \( A \) is invertible. From our analysis, we found that: - \( \text{det}(A) = -\text{det}(B) \) is true. - \( \text{det}(A) = \text{det}(B) \) is not true. ### Final Answer: The statement that is **not true** is: \[ \text{det}(A) = \text{det}(B) \]

To solve the problem, we need to analyze the matrices \( A \) and \( B \) given in the question and understand the implications of the invertibility of matrix \( A \). ### Step-by-Step Solution: 1. **Define the Matrices**: \[ A = \begin{bmatrix} a & b & c \\ ...
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