Question

What is the product of AB?
A=[0 2 1] B=[1 -4]
[-5 -1 0] [0 1]
[5 -1]

Answer 1

To multiply two matrix, you conceptually rotate B counter clockwise into A from the top.
So, in this case your result is going to be a 2x2 matrix consisting of the elements of

(A row 1 * B col 1), (A row 1 * B col 2)
(A row 2 * B col 1), (A row 2 * B col 2)