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If a matrix A=[5−8−35]A = \begin{bmatrix} 5 & -8 \\ -3 & 5 \end{bmatrix} then which of the following is / are TRUE?

(A) ∣A∣=1|A| = 1

(B) AA is a singular matrix.

(C) −2A=[10−16−610]-2A = \begin{bmatrix} 10 & -16 \\ -6 & 10 \end{bmatrix}

(D) AI=[5005]AI = \begin{bmatrix} 5 & 0 \\ 0 & 5 \end{bmatrix} II is an identity matrix of order 2.

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 1

Given: A=[5−8−35]A = \begin{bmatrix} 5 & -8 \\ -3 & 5 \end{bmatrix}

For statement (A): ∣A∣=1|A| = 1

For a matrix [abcd]\begin{bmatrix} a & b \\ c & d \end{bmatrix}, the determinant is ad−bcad - bc

∣A∣=(5)(5)−(−8)(−3)|A| = (5)(5) - (-8)(-3)

∣A∣=25−24|A| = 25 - 24

∣A∣=1|A| = 1

Statement (A) is TRUE.


For statement (B): A is a singular matrix

A matrix is singular if its determinant equals 0.

From statement (A), ∣A∣=1|A| = 1.

Since ∣A∣=1≠0|A| = 1 \neq 0, matrix A is not singular.

Statement (B) is FALSE.


For statement (C): −2A=[10−16−610]-2A = \begin{bmatrix} 10 & -16 \\ -6 & 10 \end{bmatrix}

−2A=−2×[5−8−35]-2A = -2 \times \begin{bmatrix} 5 & -8 \\ -3 & 5 \end{bmatrix}

−2A=[−2×5−2×(−8)−2×(−3)−2×5]-2A = \begin{bmatrix} -2 \times 5 & -2 \times (-8) \\ -2 \times (-3) & -2 \times 5 \end{bmatrix}

−2A=[−10166−10]-2A = \begin{bmatrix} -10 & 16 \\ 6 & -10 \end{bmatrix}

This does not equal [10−16−610]\begin{bmatrix} 10 & -16 \\ -6 & 10 \end{bmatrix}.

Statement (C) is FALSE.


For statement (D): AI=[5005]AI = \begin{bmatrix} 5 & 0 \\ 0 & 5 \end{bmatrix}

When any matrix is multiplied by an identity matrix, the result is the original matrix.

AI=AAI = A

AI=[5−8−35]AI = \begin{bmatrix} 5 & -8 \\ -3 & 5 \end{bmatrix}

This does not equal [5005]\begin{bmatrix} 5 & 0 \\ 0 & 5 \end{bmatrix}.

Statement (D) is FALSE.


Only statement (A) is TRUE.

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