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TS EAMCET · Maths · Matrices

If the matrix \(A=\left[\begin{array}{lll}1 & 2 & 2 \\ 2 & 1 & 2 \\ 2 & 2 & 1\end{array}\right]\) satisfies the matrix equation \(\mathrm{A}^2-4 \mathrm{~A}-5 \mathrm{I}=0\), then \(\mathrm{A}^{-1}=\)

  1. A \(\frac{1}{5}\left[\begin{array}{ccc}-3 & 2 & 2 \\ -2 & 3 & -2 \\ 2 & 2 & -3\end{array}\right]\)
  2. B \(\frac{1}{5}\left[\begin{array}{ccc}-3 & 2 & 2 \\ 2 & -3 & 2 \\ 2 & 2 & -3\end{array}\right]\)
  3. C \(\frac{1}{5}\left[\begin{array}{ccc}-3 & 2 & 2 \\ 2 & -3 & 2 \\ -2 & -2 & 3\end{array}\right]\)
  4. D \(\frac{1}{5}\left[\begin{array}{ccc}-3 & 2 & 2 \\ 2 & -3 & 2 \\ 2 & 2 & 3\end{array}\right]\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(\frac{1}{5}\left[\begin{array}{ccc}-3 & 2 & 2 \\ 2 & -3 & 2 \\ 2 & 2 & -3\end{array}\right]\)

Step-by-step Solution

Detailed explanation

Given matrix \(A=\left[\begin{array}{lll}1 & 2 & 2 \\ 2 & 1 & 2 \\ 2 & 2 & 1\end{array}\right]\). Multiply both sides by \(\mathrm{A}^{-1}\).…