Find the product of the following two matrices.

open square bracket,
begin matrix
row 1, column 1, 0
row 1, column 2, minus, 1
row 1, column 3, 0
row 2, column 1, minus, 5
row 2, column 2, minus, 2
row 2, column 3, minus, 5
row 3, column 1, 0
row 3, column 2, 0
row 3, column 3, 4
end matrix
, close square bracket, open square bracket,
begin matrix
row 1, column 1, 1
row 1, column 2, 0
row 1, column 3, 1
row 2, column 1, minus, 1
row 2, column 2, 0
row 2, column 3, minus, 1
row 3, column 1, 1
row 3, column 2, minus, 1
row 3, column 3, 0
end matrix
, close square bracket


0
−5
0


−1
−2
0


0
−5
4






1
−1
1


0
0
−1


1
−1
0


1 answer

To find the product of the given matrices, we will perform matrix multiplication. Let's denote the first matrix (let's call it \(A\)) and the second matrix (let's call it \(B\)):

\[ A = \begin{bmatrix} 0 & -1 & 0 \ -5 & -2 & -5 \ 0 & 0 & 4 \end{bmatrix} \]

\[ B = \begin{bmatrix} 1 & 0 & 1 \ -1 & 0 & -1 \ 1 & -1 & 0 \end{bmatrix} \]

Step 1: Dimension Check

Matrix \(A\) is of size \(3 \times 3\) and matrix \(B\) is also of size \(3 \times 3\). Hence, the resulting product \(C = A \times B\) will also be of size \(3 \times 3\).

Step 2: Perform Multiplication

The entry in the resulting matrix \(C\) at position \(C[i][j]\) is computed as follows:

\[ C[i][j] = \sum_{k=1}^{3} A[i][k] \cdot B[k][j] \]

Let's calculate each entry of the resulting matrix \(C\):

For \(C[1][1]\):

\[ C[1][1] = A[1][1] \cdot B[1][1] + A[1][2] \cdot B[2][1] + A[1][3] \cdot B[3][1] \] \[ = 0 \cdot 1 + (-1) \cdot (-1) + 0 \cdot 1 = 0 + 1 + 0 = 1 \]

For \(C[1][2]\):

\[ C[1][2] = A[1][1] \cdot B[1][2] + A[1][2] \cdot B[2][2] + A[1][3] \cdot B[3][2] \] \[ = 0 \cdot 0 + (-1) \cdot 0 + 0 \cdot (-1) = 0 + 0 + 0 = 0 \]

For \(C[1][3]\):

\[ C[1][3] = A[1][1] \cdot B[1][3] + A[1][2] \cdot B[2][3] + A[1][3] \cdot B[3][3] \] \[ = 0 \cdot 1 + (-1) \cdot (-1) + 0 \cdot 0 = 0 + 1 + 0 = 1 \]

For \(C[2][1]\):

\[ C[2][1] = A[2][1] \cdot B[1][1] + A[2][2] \cdot B[2][1] + A[2][3] \cdot B[3][1] \] \[ = (-5) \cdot 1 + (-2) \cdot (-1) + (-5) \cdot 1 = -5 + 2 - 5 = -8 \]

For \(C[2][2]\):

\[ C[2][2] = A[2][1] \cdot B[1][2] + A[2][2] \cdot B[2][2] + A[2][3] \cdot B[3][2] \] \[ = (-5) \cdot 0 + (-2) \cdot 0 + (-5) \cdot (-1) = 0 + 0 + 5 = 5 \]

For \(C[2][3]\):

\[ C[2][3] = A[2][1] \cdot B[1][3] + A[2][2] \cdot B[2][3] + A[2][3] \cdot B[3][3] \] \[ = (-5) \cdot 1 + (-2) \cdot (-1) + (-5) \cdot 0 = -5 + 2 + 0 = -3 \]

For \(C[3][1]\):

\[ C[3][1] = A[3][1] \cdot B[1][1] + A[3][2] \cdot B[2][1] + A[3][3] \cdot B[3][1] \] \[ = 0 \cdot 1 + 0 \cdot (-1) + 4 \cdot 1 = 0 + 0 + 4 = 4 \]

For \(C[3][2]\):

\[ C[3][2] = A[3][1] \cdot B[1][2] + A[3][2] \cdot B[2][2] + A[3][3] \cdot B[3][2] \] \[ = 0 \cdot 0 + 0 \cdot 0 + 4 \cdot (-1) = 0 + 0 - 4 = -4 \]

For \(C[3][3]\):

\[ C[3][3] = A[3][1] \cdot B[1][3] + A[3][2] \cdot B[2][3] + A[3][3] \cdot B[3][3] \] \[ = 0 \cdot 1 + 0 \cdot (-1) + 4 \cdot 0 = 0 + 0 + 0 = 0 \]

Step 3: Construct the Result Matrix

Combining all of the results, we get the resulting matrix \(C\):

\[ C = \begin{bmatrix} 1 & 0 & 1 \ -8 & 5 & -3 \ 4 & -4 & 0 \end{bmatrix} \]

Final Answer:

The product of the matrices \(A\) and \(B\) is:

\[ \begin{bmatrix} 1 & 0 & 1 \ -8 & 5 & -3 \ 4 & -4 & 0 \end{bmatrix} \]