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

माना \(P =\left[\begin{array}{ccc}3 & -1 & -2 \\ 2 & 0 & \alpha \\ 3 & -5 & 0\end{array}\right]\) है, जबकि \(\alpha \in R\) है। माना \(Q =\left[ q _{ ij }\right]\) एक आव्यूह है, जिसके लिए \(PQ = kI _{3}\), किसी शून्येतर, \(k \in K\) के लिए, है। यदि \(q _{23}=-\frac{ k }{8}\) तथा \(| Q |=\frac{ k ^{2}}{2}\) है, तो \(\alpha^{2}+ k ^{2}\) बराबर है

  1. A \(17\)
  2. B \(21\)
  3. C \(13\)
  4. D \(19\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(17\)

Step-by-step Solution

Detailed explanation

\(PQ = kI\) \(| P | \cdot| Q |= k ^{3}\) \(\Rightarrow| P |=2 k \neq 0 \Rightarrow P\) is an invertible matrix \(\because PQ = kI\) \(\therefore Q=k P^{-1} I\) \(\therefore Q=\frac{\text { adj.P }}{2}\) \(\because q _{23}=-\frac{ k }{8}\)…
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