Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Algebra

Question:

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

(A) $|A| = 1$
(B) A is a singular matrix.
(C) $-2A=\begin{bmatrix}10&-16\\-6&10\end{bmatrix}$
(D) $AI =\begin{bmatrix}5&0\\0&5\end{bmatrix}$, I is an identity matrix of order 2.

Choose the correct answer from the options given below:

Options:

(A) only

(A) and (C) only

(A), (B) and (C) only

(A), (B), (C) and (D) only

Correct Answer:

(A) only

Explanation:

The correct answer is Option (1) → (A) only

$|A|=5\cdot5-(-8)(-3)=25-24=1$

$A$ is not singular (determinant $\neq 0$)

$-2A=\begin{pmatrix}-10 & 16\\ 6 & -10\end{pmatrix}\neq\begin{pmatrix}10 & -16\\ -6 & 10\end{pmatrix}$

$AI=A\neq\begin{pmatrix}5 & 0\\ 0 & 5\end{pmatrix}$

Only (A) is true.