COMEDK · Maths · 21. Matrices
Given the matrices \(A = \begin{bmatrix} 1 & 0 & 1 \\ 0 & 1 & 0 \\ 1 & 0 & 2 \end{bmatrix}\) and \(B = \begin{bmatrix} 2 & 1 & 0 \\ 1 & 1 & 2 \\ 0 & 2 & 1 \end{bmatrix}\), then the minor \(M_{23}\) of the matrix \((A B^{-1})^{-1}\) is:
- A \(4\)
- B \(2\)
- C \(9\)
- D \(-9\)
Answer & Solution
Correct Answer
(C) \(9\)
Step-by-step Solution
Detailed explanation
Let \(C = (A B^{-1})^{-1}\). Using the reversal law for matrix inverses, we have: \(C = (B^{-1})^{-1} A^{-1} = B A^{-1}\) First, we find the inverse of matrix \(A\). The determinant of \(A\) is: \(|A| = 1(2 - 0) - 0 + 1(0 - 1) = 1\) The adjugate matrix of \(A\) is the transpose…
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