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AP EAMCET · 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 matrix \(A\) and \(\operatorname{det} A=4\), then the value of \(\alpha\) is

  1. A \(3\)
  2. B \(22\)
  3. C \(11\)
  4. D \(4\)
Verified Solution

Answer & Solution

Correct Answer

(C) \(11\)

Step-by-step Solution

Detailed explanation

\( \operatorname{det} P = 1(12-12) - \alpha(4-6) + 3(4-6) = 2\alpha - 6 \) \( \operatorname{det}(\operatorname{adj} A) = (\operatorname{det} A)^{n-1} \) \( 2\alpha - 6 = (4)^{3-1} = 16 \) \( 2\alpha = 22 \) \( \alpha = 11 \)