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MHT CET · Maths · Matrices

If \(P=\left[\begin{array}{lll}1 & \alpha & 3 \\ 1 & 3 & 3 \\ 2 & 4 & 4\end{array}\right]\) is the adjoint of a \(3 \times 3\) matrix A and \(|A|=4\), then value of \(\alpha\) is

  1. A \(4\)
  2. B \(11\)
  3. C \(5\)
  4. D \(0\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(11\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned} & P=\operatorname{adj} A \\ \therefore \quad & |\mathrm{P}|=|\mathrm{A}|^2 \\ & \Rightarrow\left|\begin{array}{lll}1 & \alpha & 3 \\ 1 & 3 & 3 \\ 2 & 4 & 4\end{array}\right|=4^2 \\ & \Rightarrow 2 \alpha-6=16 \\ & \Rightarrow \alpha=11\end{aligned}\)
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