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CUET · MATHS · PYQ PAPER 2023

If \(A=\left[\begin{array}{cc}1 & 0 \\ -1 & 7\end{array}\right]\) and \(A^2-8 A+K I=O\), then the value of \(K\) is:

  1. A 5
  2. B 6
  3. C -7
  4. D 7
Verified Solution

Answer & Solution

Correct Answer

(D) 7

Step-by-step Solution

Detailed explanation

\( \text{Tr}(A) = 1+7 = 8 \) \( \text{det}(A) = 1(7) - 0(-1) = 7 \) \( A^2 - \text{Tr}(A)A + \text{det}(A)I = O \Rightarrow A^2 - 8A + 7I = O \) \( K = 7 \)