14. Given the following matrices, what is the correct product matrix [tex]\(AB\)[/tex]?

[tex]\( A = \left[\begin{array}{ll}1 & 2 \\ 3 & 4\end{array}\right] \)[/tex]

[tex]\( B = \left[\begin{array}{cc}-1 & 2 \\ 1 & 0\end{array}\right] \)[/tex]

A. [tex]\(\left[\begin{array}{lll}5 & 9 & 7\end{array}\right]\)[/tex]

B. [tex]\(\left[\begin{array}{cc}2 & -4 \\ 4 & 0 \\ 1 & 7\end{array}\right]\)[/tex]

C. [tex]\(\left[\begin{array}{ll}1 & 2 \\ 1 & 6\end{array}\right]\)[/tex]

D. [tex]\(\left[\begin{array}{ll}5 & 6 \\ 1 & 2\end{array}\right]\)[/tex]

E. [tex]\(\left[\begin{array}{ll}0 & 4 \\ 4 & 4\end{array}\right]\)[/tex]

F. [tex]\(\left[\begin{array}{cc}-1 & 4 \\ 3 & 0\end{array}\right]\)[/tex]



Answer :

To determine the product of matrices [tex]\( A \)[/tex] and [tex]\( B \)[/tex], we need to perform matrix multiplication. Given the matrices:

[tex]\[ A = \left[\begin{array}{cc}1 & 2 \\ 3 & 4\end{array}\right] \quad \text{and} \quad B = \left[\begin{array}{cc}-1 & 2 \\ 1 & 0\end{array}\right], \][/tex]

we will calculate the product matrix [tex]\( AB = C \)[/tex].

Matrix [tex]\( C \)[/tex] will also be a [tex]\( 2 \times 2 \)[/tex] matrix, and to find each entry [tex]\( c_{ij} \)[/tex] of matrix [tex]\( C \)[/tex], we use the dot product of the [tex]\( i \)[/tex]-th row of [tex]\( A \)[/tex] with the [tex]\( j \)[/tex]-th column of [tex]\( B \)[/tex].

1. For the entry [tex]\( c_{11} \)[/tex] (first row, first column):
[tex]\[ c_{11} = (1 \cdot -1) + (2 \cdot 1) = -1 + 2 = 1 \][/tex]

2. For the entry [tex]\( c_{12} \)[/tex] (first row, second column):
[tex]\[ c_{12} = (1 \cdot 2) + (2 \cdot 0) = 2 + 0 = 2 \][/tex]

3. For the entry [tex]\( c_{21} \)[/tex] (second row, first column):
[tex]\[ c_{21} = (3 \cdot -1) + (4 \cdot 1) = -3 + 4 = 1 \][/tex]

4. For the entry [tex]\( c_{22} \)[/tex] (second row, second column):
[tex]\[ c_{22} = (3 \cdot 2) + (4 \cdot 0) = 6 + 0 = 6 \][/tex]

Thus, the product matrix [tex]\( AB = C \)[/tex] is:

[tex]\[ C = \left[\begin{array}{cc}1 & 2 \\ 1 & 6\end{array}\right] \][/tex]

Therefore, the correct product matrix is:
[tex]\[ \left[\begin{array}{cc}1 & 2 \\ 1 & 6\end{array}\right] \][/tex]

So, the correct answer is option D:

[tex]\[ \left[\begin{array}{ll}1 & 2 \\ 1 & 6\end{array}\right] \][/tex]