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
- A \(4\)
- B \(11\)
- C \(5\)
- D \(0\)
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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