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CUET · MATHS · PYQ PAPER 2025

If \(A=\left[\begin{array}{ccc}a & 1 & -1 \\ 0 & b & 4 \\ 4 & 4 & c\end{array}\right]\) and \(a b c=12, b=4 a\), find the value of \(|A(\operatorname{adj} A)|\)

  1. A \(28^3\)
  2. B \(12^3\)
  3. C \(28^2\)
  4. D \(48^2\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(28^3\)

Step-by-step Solution

Detailed explanation

\(|A(\operatorname{adj} A)| = |A|^3\) \(|A| = a(bc - 16) - 1(0c - 16) - 1(0 \cdot 4 - 4b)\) \(|A| = abc - 16a + 16 + 4b\) \(|A| = 12 - 16a + 16 + 4(4a)\) \(|A| = 12 - 16a + 16 + 16a = 28\) \(|A(\operatorname{adj} A)| = 28^3\)
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