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If A = [{:(2, x - 2),(2x +3, x -3):}] is...

If A = `[{:(2, x - 2),(2x +3, x -3):}]` is a symmetric matrix, then the value of x is

A

4

B

3

C

`-5`

D

`-3`

Text Solution

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The correct Answer is:
To determine the value of \( x \) for which the matrix \[ A = \begin{pmatrix} 2 & x - 2 \\ 2x + 3 & x - 3 \end{pmatrix} \] is symmetric, we need to use the property that a matrix is symmetric if it is equal to its transpose, i.e., \( A = A^T \). ### Step-by-step Solution: 1. **Write down the matrix \( A \)**: \[ A = \begin{pmatrix} 2 & x - 2 \\ 2x + 3 & x - 3 \end{pmatrix} \] 2. **Find the transpose of matrix \( A \)**: The transpose of a matrix is obtained by swapping its rows with columns. Therefore, \[ A^T = \begin{pmatrix} 2 & 2x + 3 \\ x - 2 & x - 3 \end{pmatrix} \] 3. **Set the matrix \( A \) equal to its transpose \( A^T \)**: \[ \begin{pmatrix} 2 & x - 2 \\ 2x + 3 & x - 3 \end{pmatrix} = \begin{pmatrix} 2 & 2x + 3 \\ x - 2 & x - 3 \end{pmatrix} \] 4. **Equate corresponding elements**: From the equality of the matrices, we get the following equations: - From the first row, first column: \( 2 = 2 \) (which is always true). - From the first row, second column: \( x - 2 = 2x + 3 \) - From the second row, first column: \( 2x + 3 = x - 2 \) - From the second row, second column: \( x - 3 = x - 3 \) (which is also always true). 5. **Solve the first equation**: \[ x - 2 = 2x + 3 \] Rearranging gives: \[ x - 2x = 3 + 2 \implies -x = 5 \implies x = -5 \] 6. **Verify with the second equation**: \[ 2x + 3 = x - 2 \] Substitute \( x = -5 \): \[ 2(-5) + 3 = -5 - 2 \implies -10 + 3 = -5 - 2 \implies -7 = -7 \text{ (True)} \] 7. **Conclusion**: The value of \( x \) for which the matrix \( A \) is symmetric is: \[ \boxed{-5} \]
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