Question

Find the product. [5 5 [-4 9

-2 3] 8 7]

Answer 1

(a)

`\left[\begin{array}{cc}20&80\\32&3\end{array}\right]`

Explanation:

You want the product of the given 2×2 matrices.

Solution

The value at any given (row, column) of the result matrix is the dot product of the corresponding row of the first matrix with the corresponding column of the second matrix.

For example, row 2 column 1 of the result will be the dot product of row 2 of the left matrix with column 1 of the right matrix:

[-2, 3]·[-4, 8] = (-2)(-4) +(3)(8) = 8 +24 = 32

This is sufficient to identify the first answer choice as the correct one.

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Additional comment

A suitable calculator can compute the entire product for you, as in the attachment.