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JEE Mains · Maths · STD 12 - 3 and 4 . metrices and determinant

माना \(\mathrm{A}=\left[\begin{array}{lll}1 & 0 & 0 \\ 0 & \alpha & \beta \\ 0 & \beta & \alpha\end{array}\right]\) तथा \(|2 \mathrm{~A}|^3=2^{21}\) है, जहाँ \(\alpha, \beta \in \mathrm{Z}\) है। तो \(\alpha\) का एक मान ........... है।

  1. A \(3\)
  2. B \(5\)
  3. C \(17\)
  4. D \(9\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(5\)

Step-by-step Solution

Detailed explanation

\( |A|=\alpha^2-\beta^2 \) \( |2 A|^3=2^{21} \Rightarrow|A|=2^4 \) \( \alpha^2-\beta^2=16 \) \( (\alpha+\beta)(\alpha-\beta)=16 \Rightarrow \alpha=4 \text { or } 5\)
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