Target Exam

CUET

Subject

-- Applied Mathematics - Section B2

Chapter

Algebra

Question:

Which of the following statements are correct?

(A) If A is a square matrix, then $|A^2|=|A|^2$.
(B) If A and B are square matrices of the same order, then $\text{det (AB) = det (A) + det (B)}$.
(C) If A is a square matrix of order 3 and $|A|=2$, then the value of $|-3A|$ is 54.
(D) If the matrix $\begin{bmatrix}5-x&x-1\\3&5\end{bmatrix}$ is singular, then the value of $x$ is 7/2.

Choose the correct answer from the options given below:

Options:

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

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

(A) and (D) only

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

Correct Answer:

(A) and (D) only

Explanation:

The correct answer is Option (3) → (A) and (D) only

Check each statement:

(A) If $A$ is square, $|A^2| = |A|^2 ✅$ (True)

(B) For square matrices, $\det(AB) = \det(A) \cdot \det(B) ❌$ (False, not sum)

(C) $A$ is order 3, $|A| = 2$, then $|-3A| = (-3)^3 |A| = -27*2 = -54 ❌$

(D) Matrix $\begin{bmatrix} 5-x & x-1 \\ 3 & 5 \end{bmatrix}$ is singular → determinant = 0

Determinant: $(5-x)(5) - (x-1)(3) = 25 - 5x - 3x + 3 = 28 - 8x = 0$

$x = \frac{28}{8} = \frac{7}{2} ✅$