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Let A be a $$3 \times 3$$ matrix such that
$$A\begin{bmatrix} 1 & 2 & 3 \\ 0 & 2 & 3 \\ 0 & 1 & 1 \end{bmatrix} = \begin{bmatrix} 0 & 0 & 1 \\ 1 & 0 & 0 \\ 0 & 1 & 0 \end{bmatrix}$$
Then A$$^{-1}$$ is:
We are given the matrix equation:
$$A \begin{bmatrix} 1 & 2 & 3 \\ 0 & 2 & 3 \\ 0 & 1 & 1 \end{bmatrix} = \begin{bmatrix} 0 & 0 & 1 \\ 1 & 0 & 0 \\ 0 & 1 & 0 \end{bmatrix}$$
Let us denote the matrix on the left as $$ B $$, so:
$$B = \begin{bmatrix} 1 & 2 & 3 \\ 0 & 2 & 3 \\ 0 & 1 & 1 \end{bmatrix}$$
And the matrix on the right as $$ C $$, so:
$$C = \begin{bmatrix} 0 & 0 & 1 \\ 1 & 0 & 0 \\ 0 & 1 & 0 \end{bmatrix}$$
The equation becomes $$ A B = C $$. To find $$ A^{-1} $$, we rearrange the equation. Multiplying both sides on the right by $$ B^{-1} $$ gives $$ A = C B^{-1} $$. Then, taking the inverse of both sides:
$$A^{-1} = (C B^{-1})^{-1} = B C^{-1}$$
So, we need to compute $$ B C^{-1} $$. First, we find $$ C^{-1} $$. Notice that $$ C $$ is a permutation matrix that cycles the rows: applying $$ C $$ to a vector $$ \begin{bmatrix} x \\ y \\ z \end{bmatrix} $$ gives $$ \begin{bmatrix} z \\ x \\ y \end{bmatrix} $$. The inverse permutation should map $$ \begin{bmatrix} z \\ x \\ y \end{bmatrix} $$ back to $$ \begin{bmatrix} x \\ y \\ z \end{bmatrix} $$, which corresponds to the matrix:
$$C^{-1} = \begin{bmatrix} 0 & 1 & 0 \\ 0 & 0 & 1 \\ 1 & 0 & 0 \end{bmatrix}$$
Verification:
$$C^{-1} \begin{bmatrix} z \\ x \\ y \end{bmatrix} = \begin{bmatrix} 0 & 1 & 0 \\ 0 & 0 & 1 \\ 1 & 0 & 0 \end{bmatrix} \begin{bmatrix} z \\ x \\ y \end{bmatrix} = \begin{bmatrix} x \\ y \\ z \end{bmatrix}$$
Now, we compute $$ B C^{-1} $$:
$$B = \begin{bmatrix} 1 & 2 & 3 \\ 0 & 2 & 3 \\ 0 & 1 & 1 \end{bmatrix}, \quad C^{-1} = \begin{bmatrix} 0 & 1 & 0 \\ 0 & 0 & 1 \\ 1 & 0 & 0 \end{bmatrix}$$
Perform matrix multiplication:
Element at row 1, column 1: $$ (1)(0) + (2)(0) + (3)(1) = 0 + 0 + 3 = 3 $$
Element at row 1, column 2: $$ (1)(1) + (2)(0) + (3)(0) = 1 + 0 + 0 = 1 $$
Element at row 1, column 3: $$ (1)(0) + (2)(1) + (3)(0) = 0 + 2 + 0 = 2 $$
Element at row 2, column 1: $$ (0)(0) + (2)(0) + (3)(1) = 0 + 0 + 3 = 3 $$
Element at row 2, column 2: $$ (0)(1) + (2)(0) + (3)(0) = 0 + 0 + 0 = 0 $$
Element at row 2, column 3: $$ (0)(0) + (2)(1) + (3)(0) = 0 + 2 + 0 = 2 $$
Element at row 3, column 1: $$ (0)(0) + (1)(0) + (1)(1) = 0 + 0 + 1 = 1 $$
Element at row 3, column 2: $$ (0)(1) + (1)(0) + (1)(0) = 0 + 0 + 0 = 0 $$
Element at row 3, column 3: $$ (0)(0) + (1)(1) + (1)(0) = 0 + 1 + 0 = 1 $$
So, the product is:
$$B C^{-1} = \begin{bmatrix} 3 & 1 & 2 \\ 3 & 0 & 2 \\ 1 & 0 & 1 \end{bmatrix}$$
Therefore, $$ A^{-1} = \begin{bmatrix} 3 & 1 & 2 \\ 3 & 0 & 2 \\ 1 & 0 & 1 \end{bmatrix} $$.
Comparing with the options:
Option A: $$ \begin{bmatrix} 3 & 1 & 2 \\ 3 & 0 & 2 \\ 1 & 0 & 1 \end{bmatrix} $$
Option B: $$ \begin{bmatrix} 3 & 2 & 1 \\ 3 & 2 & 0 \\ 1 & 1 & 0 \end{bmatrix} $$
Option C: $$ \begin{bmatrix} 0 & 1 & 3 \\ 0 & 2 & 3 \\ 1 & 1 & 1 \end{bmatrix} $$
Option D: $$ \begin{bmatrix} 1 & 2 & 3 \\ 0 & 1 & 1 \\ 0 & 2 & 3 \end{bmatrix} $$
Our result matches Option A.
Hence, the correct answer is Option A.
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