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Matrix A and Matrix B, defined below, are inverse matrices.

[tex]\[ A=\left[\begin{array}{lr}
2 & -6 \\
1 & -1
\end{array}\right] \quad B=\left[\begin{array}{cc}
-3 & 2 \\
2 & -1
\end{array}\right] \][/tex]

A. True
B. False


Sagot :

To determine whether matrices [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are inverses of each other, we need to compute their product and verify if the result is the identity matrix.

Given:
[tex]\[ A = \begin{bmatrix} 2 & -6 \\ 1 & -1 \end{bmatrix} \][/tex]
[tex]\[ B = \begin{bmatrix} -3 & 2 \\ 2 & -1 \end{bmatrix} \][/tex]

First, let's calculate the product [tex]\( A \cdot B \)[/tex]:

[tex]\[ A \cdot B = \begin{bmatrix} 2 & -6 \\ 1 & -1 \end{bmatrix} \cdot \begin{bmatrix} -3 & 2 \\ 2 & -1 \end{bmatrix} \][/tex]

We'll multiply the matrices step by step:

The element at the first row, first column of the product:
[tex]\[ (2 \times -3) + (-6 \times 2) = -6 + (-12) = -18 \][/tex]

The element at the first row, second column of the product:
[tex]\[ (2 \times 2) + (-6 \times -1) = 4 + 6 = 10 \][/tex]

The element at the second row, first column of the product:
[tex]\[ (1 \times -3) + (-1 \times 2) = -3 + (-2) = -5 \][/tex]

The element at the second row, second column of the product:
[tex]\[ (1 \times 2) + (-1 \times -1) = 2 + 1 = 3 \][/tex]

Therefore, the product of [tex]\( A \)[/tex] and [tex]\( B \)[/tex] is:
[tex]\[ A \cdot B = \begin{bmatrix} -18 & 10 \\ -5 & 3 \end{bmatrix} \][/tex]

The identity matrix for 2x2 matrices is:
[tex]\[ I = \begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix} \][/tex]

Since:
[tex]\[ A \cdot B \ne I = \begin{bmatrix} -18 & 10 \\ -5 & 3 \end{bmatrix} \ne \begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix} \][/tex]

Thus, the product [tex]\( A \cdot B \)[/tex] is not the identity matrix.

Therefore, matrices [tex]\( A \)[/tex] and [tex]\( B \)[/tex] are not inverse matrices.

The correct answer is:

False