Solved on Nov 06, 2023

Find the inverse A1A^{-1} of the given 3x3 matrix A=[113216031]A = \begin{bmatrix} 1 & 1 & 3 \\ -2 & -1 & -6 \\ 0 & 3 & 1 \end{bmatrix}.

STEP 1

Assumptions1. The given matrix is a3x3 matrix A=[11316031]A = \begin{bmatrix}1 &1 &3 \\ - & -1 & -6 \\0 &3 &1 \end{bmatrix} . We are asked to find the inverse of matrix A, denoted as A1A^{-1}

STEP 2

To find the inverse of a matrix, we first need to create an augmented matrix by appending the identity matrix to the given matrix. The identity matrix is a square matrix with ones on the diagonal and zeros elsewhere.
[A]=[1110021601001001][A|] = \left[\begin{array}{ccc|ccc}1 &1 & &1 &0 &0 \\ -2 & -1 & -6 &0 &1 &0 \\0 & &1 &0 &0 &1 \end{array}\right]

STEP 3

Next, we perform row operations to transform the left side of the augmented matrix into the identity matrix. The goal is to get a diagonal of ones and zeros everywhere else on the left side of the augmented matrix.
First, we swap row1 and row2 to get a1 in the top left corner.
[216010113100031001]\left[\begin{array}{ccc|ccc} -2 & -1 & -6 &0 &1 &0 \\1 &1 &3 &1 &0 &0 \\0 &3 &1 &0 &0 &1 \end{array}\right]

STEP 4

Multiply the first row by -1/2 to get a1 in the top left corner.
[10.300.0113100031001]\left[\begin{array}{ccc|ccc}1 &0. &3 &0 & -0. &0 \\1 &1 &3 &1 &0 &0 \\0 &3 &1 &0 &0 &1 \end{array}\right]

STEP 5

Subtract the first row from the second row to get a0 in the second row, first column.
[10.5300.5000.5010.50031001]\left[\begin{array}{ccc|ccc}1 &0.5 &3 &0 & -0.5 &0 \\0 &0.5 &0 &1 &0.5 &0 \\0 &3 &1 &0 &0 &1 \end{array}\right]

STEP 6

Subtract6 times the second row from the first row to get a0 in the first row, second column.
[10363000.5010.50031001]\left[\begin{array}{ccc|ccc}1 &0 &3 & -6 & -3 &0 \\0 &0.5 &0 &1 &0.5 &0 \\0 &3 &1 &0 &0 &1 \end{array}\right]

STEP 7

Multiply the second row by2 to get a1 in the second row, second column.
[103630010210031001]\left[\begin{array}{ccc|ccc}1 &0 &3 & -6 & -3 &0 \\0 &1 &0 &2 &1 &0 \\0 &3 &1 &0 &0 &1 \end{array}\right]

STEP 8

Subtract3 times the second row from the third row to get a0 in the third row, second column.
[103630010210001631]\left[\begin{array}{ccc|ccc}1 &0 &3 & -6 & -3 &0 \\0 &1 &0 &2 &1 &0 \\0 &0 &1 & -6 & -3 &1 \end{array}\right]

STEP 9

Subtract3 times the third row from the first row to get a in the first row, third column.
[1263263]\left[\begin{array}{ccc|ccc} & & &12 &6 & -3 \\ & & &2 & & \\ & & & -6 & -3 & \end{array}\right]

STEP 10

Now, the left side of the augmented matrix is the identity matrix. The right side of the augmented matrix is the inverse of the original matrix.
A=[12632063]A^{-} = \begin{bmatrix}12 &6 & -3 \\2 & &0 \\ -6 & -3 & \end{bmatrix}So, the inverse of matrix A is A=[12632063]A^{-} = \begin{bmatrix}12 &6 & -3 \\2 & &0 \\ -6 & -3 & \end{bmatrix}.

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