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For [tex]\(A=\left[\begin{array}{rr}1 & 7 \\ -3 & 2\end{array}\right]\)[/tex] and [tex]\(B=\left[\begin{array}{rr}6 & 0 \\ 1 & -2\end{array}\right]\)[/tex], find

(a) [tex]\(A B\)[/tex]

(b) [tex]\(B A\)[/tex]

(a) [tex]\(A B =\)[/tex]

Sagot :

Sure, let's calculate the matrix product [tex]\( AB \)[/tex] for the given matrices [tex]\( A \)[/tex] and [tex]\( B \)[/tex].

Given:
[tex]\[ A = \begin{bmatrix} 1 & 7 \\ -3 & 2 \end{bmatrix} \][/tex]
[tex]\[ B = \begin{bmatrix} 6 & 0 \\ 1 & -2 \end{bmatrix} \][/tex]

To find the product [tex]\( AB \)[/tex], we need to perform matrix multiplication. The element in the first row and first column of [tex]\( AB \)[/tex] is calculated by taking the dot product of the first row of [tex]\( A \)[/tex] and the first column of [tex]\( B \)[/tex]. Similarly, we will calculate the other elements.

1. Element (1,1) of [tex]\( AB \)[/tex]:
[tex]\[ (1 \times 6) + (7 \times 1) = 6 + 7 = 13 \][/tex]

2. Element (1,2) of [tex]\( AB \)[/tex]:
[tex]\[ (1 \times 0) + (7 \times -2) = 0 - 14 = -14 \][/tex]

3. Element (2,1) of [tex]\( AB \)[/tex]:
[tex]\[ (-3 \times 6) + (2 \times 1) = -18 + 2 = -16 \][/tex]

4. Element (2,2) of [tex]\( AB \)[/tex]:
[tex]\[ (-3 \times 0) + (2 \times -2) = 0 - 4 = -4 \][/tex]

Now, putting all these elements together, we get:
[tex]\[ AB = \begin{bmatrix} 13 & -14 \\ -16 & -4 \end{bmatrix} \][/tex]

So, the product [tex]\( AB \)[/tex] is:
[tex]\[ \begin{bmatrix} 13 & -14 \\ -16 & -4 \end{bmatrix} \][/tex]