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Let A be a matrix such that A=[12−23]A = \begin{bmatrix} 1 & 2 \\ -2 & 3 \end{bmatrix}. Then which of the following are TRUE?

(A) A is non-singular matrix

(B) AT=AA^T = A

(C) A is not invertible matrix

(D) A is not skew-symmetric matrix

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

Given A=[12−23]A = \begin{bmatrix} 1 & 2 \\ -2 & 3 \end{bmatrix}


Checking Statement (A): A is non-singular matrix

A matrix is non-singular if its determinant ≠ 0.

For a 2×2 matrix [abcd]\begin{bmatrix} a & b \\ c & d \end{bmatrix}, determinant = ad - bc

det(A)=(1)(3)−(2)(−2)\text{det}(A) = (1)(3) - (2)(-2)

=3+4= 3 + 4

=7= 7

Since det(A) = 7 ≠ 0, A is non-singular.

Statement (A) is TRUE.


Checking Statement (B): AT=AA^T = A

The transpose of A is:

AT=[1−223]A^T = \begin{bmatrix} 1 & -2 \\ 2 & 3 \end{bmatrix}

Comparing with A=[12−23]A = \begin{bmatrix} 1 & 2 \\ -2 & 3 \end{bmatrix}:

AT≠AA^T ≠ A

Statement (B) is FALSE.


Checking Statement (C): A is not invertible matrix

A matrix is invertible if and only if det(A) ≠ 0.

From Statement (A), det(A) = 7 ≠ 0.

Therefore, A is invertible.

Statement (C) is FALSE.


Checking Statement (D): A is not skew-symmetric matrix

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

−A=[−1−22−3]-A = \begin{bmatrix} -1 & -2 \\ 2 & -3 \end{bmatrix}

AT=[1−223]A^T = \begin{bmatrix} 1 & -2 \\ 2 & 3 \end{bmatrix}

Since AT≠−AA^T ≠ -A, A is not skew-symmetric.

Statement (D) is TRUE.


Statements (A) and (D) are TRUE.

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