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CUET · MATHS · PYQ PAPER 2025

If \(\mathbf{A}=\left[\begin{array}{ccc}0 & 0 & \sqrt{7} \\ 0 & \sqrt{7} & 0 \\ \sqrt{7} & 0 & 0\end{array}\right]\), then \(|\operatorname{adj} \mathbf{A}|\) is equal to

  1. A 7
  2. B 49
  3. C 343
  4. D 0
Verified Solution

Answer & Solution

Correct Answer

(C) 343

Step-by-step Solution

Detailed explanation

\(|\mathbf{A}| = 0(0-0) - 0(0-0) + \sqrt{7}(0-7)\) \(|\mathbf{A}| = -7\sqrt{7}\) \(|\operatorname{adj} \mathbf{A}| = |\mathbf{A}|^{3-1} = |\mathbf{A}|^2\) \(|\operatorname{adj} \mathbf{A}| = (-7\sqrt{7})^2 = 49 \cdot 7 = 343\)