Question 441330
<font color=black size=3>
I don't recommend using and/or memorizing the formula the tutor Edwin mentioned.


Instead it is better to highlight the first row of matrix A and first column of matrix B.


We'll align the terms like so
<table border = "1" cellpadding = "5"><tr><td>row1 of A:</td><td>2</td><td>3</td><td>0</td></tr><tr><td>column1 of B:</td><td>-1</td><td>3</td><td>0</td></tr></table>


Multiply straight down (eg: 2*(-1) = -2)
<table border = "1" cellpadding = "5"><tr><td>row1 of A:</td><td>2</td><td>3</td><td>0</td></tr><tr><td>column1 of B:</td><td>-1</td><td>3</td><td>0</td></tr><tr><td>Product:</td><td>-2</td><td>9</td><td>0</td></tr></table>
Then add up the products to get -2+9+0 = 7


This result of 7 is the entry in the answer matrix that is in the first row and first column.


The answer is of the format {{{(matrix(3,3,7,b,c,d,e,f,g,h,i))}}}


Follow this thought process for the other entries.


For instance, the 2nd row and 3rd column of the answer will involve row2 of A and column3 of B.
Let me know if you have further questions.


--------------------------


Here's a similar example
<img width="400px" src = "https://miro.medium.com/v2/resize:fit:1100/format:webp/1*YGcMQSr0ge_DGn96WnEkZw.png">
Image Source:
<a href="https://towardsdatascience.com/a-complete-beginners-guide-to-matrix-multiplication-for-data-science-with-python-numpy-9274ecfc1dc6">https://towardsdatascience.com/a-complete-beginners-guide-to-matrix-multiplication-for-data-science-with-python-numpy-9274ecfc1dc6</a>



-----------------------


Another example
<img src = "https://www.mathsisfun.com/algebra/images/matrix-multiply-b.svg">
Image Source
<a href = "https://www.mathsisfun.com/algebra/matrix-multiplying.html">https://www.mathsisfun.com/algebra/matrix-multiplying.html</a>
The scratch work highlighted in yellow would be something like this
1*8 + 2*10 + 3*12 = 8 + 20 + 36 = 64
</font>