Target Exam

CUET

Subject

-- Mathematics - Section B1

Chapter

Determinants

Question:

Let A be any square matrix of order n, then which of the following are true?

(A) $|adj\, A| = |A|^{n-1}$
(B) $|A^{-1}|=\frac{1}{|A|}$
(C) $|adj\, A| = |A|^n$
(D) $(A^T)^{-1}= (A^{-1})^T$

Choose the correct answer from the options given below:

Options:

(A) and (B) only

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

(C) and (D) only

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

Correct Answer:

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

Explanation:

The correct answer is Option (2) → (A), (B) and (D) only

(A) $|\text{adj }A| = |A|^{\,n-1}$

This is a standard identity for any square matrix of order $n$.

(A) is true.

(B) $|A^{-1}| = \frac{1}{|A|}$

Determinant of inverse is reciprocal of determinant.

(B) is true.

(C) $|\text{adj }A| = |A|^{\,n}$

This is wrong: the correct formula is $|\text{adj }A| = |A|^{\,n-1}$.

(C) is false.

(D) $(A^{T})^{-1} = (A^{-1})^{\,T}$

Inverse and transpose commute for any invertible matrix.

(D) is true.

The true statements are (A), (B), and (D).