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CUET · MATHS · PYQ PAPER 2023

If \(A=\left[\begin{array}{lll}a & 0 & 0 \\ 0 & a & 0 \\ 0 & 0 & a\end{array}\right], a \neq 0\) then \(|\operatorname{adj} A|\) is equal to

  1. A \(a ^3\)
  2. B \(a ^9\)
  3. C \(a ^6\)
  4. D \(a ^{27}\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(a ^6\)

Step-by-step Solution

Detailed explanation

\(|A| = \det\left(\left[\begin{array}{lll}a & 0 & 0 \\ 0 & a & 0 \\ 0 & 0 & a\end{array}\right]\right) = a^3\) \(|\operatorname{adj} A| = |A|^{n-1}\) \(|\operatorname{adj} A| = (a^3)^{3-1} = (a^3)^2 = a^6\)
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