Problem 1069

Find the following matrix product, if possible.

\begin{bmatrix}  5 &  -2\\  -4 & 3\\  \end{bmatrix} \begin{bmatrix}  1\\  0  \end{bmatrix}

 

Solution:-

 

Let A be an m × n matrix and let B be an n × k matrix. To find the element in the ith row and jth column of the product matrix AB, multiply each element in the ith row of A by the corresponding element in the jth column of B, and then add these products. The product matrix AB is an m × k matrix.

Let A = \begin{bmatrix}  5 &  -2\\  -4 & 3\\  \end{bmatrix}

And B = \begin{bmatrix}  1\\  0  \end{bmatrix}

In order to find the entry in the first row and first column of AB, multiply the elements of the first row of A and the corresponding elements of the column of B.

(5)*(1) + (-2)*(0) = 5

Thus, 5 is the first-row entry of the product matrix AB.

Next, multiply the elements of the second row of A and the corresponding elements of B.

(-4)*(1)+(3)*(0) = -4

The second-row entry of the product matrix AB is -4.

Now write the elements of the product AB inn matrix form.

AB = \begin{bmatrix}  5\\  -4  \end{bmatrix}

Therefore,

\begin{bmatrix}  5 &  -2\\  -4 & 3\\  \end{bmatrix}\begin{bmatrix}  1\\  0  \end{bmatrix} =  \begin{bmatrix}  5\\  -4  \end{bmatrix}

 

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