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If the matrix [014x −10−525y]\begin{bmatrix} 0 & 1 & 4x\ \\ -1 & 0 & -5 \\ 2 & 5 & y \end{bmatrix} is skew-symmetric, then

Solution

✅ Correct Option: 2

A matrix is skew-symmetric when AT=−AA^T = -A.

For a skew-symmetric matrix, all diagonal elements must be zero, and aij=−ajia_{ij} = -a_{ji}.


Given matrix: A=[014x−10−525y]A = \begin{bmatrix} 0 & 1 & 4x\\ -1 & 0 & -5 \\ 2 & 5 & y \end{bmatrix}

The transpose of matrix AA is:

AT=[0−121054x−5y]A^T = \begin{bmatrix} 0 & -1 & 2\\ 1 & 0 & 5 \\ 4x & -5 & y \end{bmatrix}


For skew-symmetric, AT=−AA^T = -A:

−A=[0−1−4x105−2−5−y]-A = \begin{bmatrix} 0 & -1 & -4x\\ 1 & 0 & 5 \\ -2 & -5 & -y \end{bmatrix}


Comparing element (1,3) from ATA^T and −A-A:

2=−4x2 = -4x

4x=−24x = -2

x=−12x = -\dfrac{1}{2}


Comparing element (3,3) from ATA^T and −A-A:

y=−yy = -y

2y=02y = 0

y=0y = 0


Therefore, x=−12x = -\dfrac{1}{2} and y=0y = 0.

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