SOLUTION: A =[-2 1 2 4 ] B= [4 -3 0 -2 3 5] (0.4)BA=?

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Question 1161697: A =[-2 1
2 4 ]
B= [4 -3
0 -2
3 5]
(0.4)BA=?
Answer by Edwin McCravy(20060) About Me  (Show Source):
You can put this solution on YOUR website!
matrix%281%2C3%2CA%2C%22%22=%22%22%2C%28matrix%282%2C2%2C-2%2C1%2C2%2C4%29%29%29

matrix%281%2C3%2CB%2C%22%22=%22%22%2C%28matrix%283%2C2%2C4%2C-3%2C0%2C-2%2C3%2C5%29%29%29

The dimension of a matrix is "down by across".

So the dimension of A is 2×2
And the dimension of B is 3×2

We can mutiply B by A because if you put their dimensions
down side by side:  

3×2 and 2×2 

the middle two 2 (in red) are the same.  And the outer 3 and 2  
(in green) tell us the dimensions of the product which are 3×2.

So 

0.4BA%22%22=%22%220.4%28matrix%283%2C2%2C4%2C-3%2C0%2C-2%2C3%2C5%29%29%22%22%2A%22%22%28matrix%282%2C2%2C-2%2C1%2C2%2C4%29%29%22%22=%22%220.4%28matrix%283%2C2%2C%22%3F%22%2C%22%3F%22%2C%22%3F%22%2C%22%3F%22%2C%22%3F%22%2C23%29%29%22%22=%22%22%28matrix%283%2C2%2C%22%3F%22%2C%22%3F%22%2C%22%3F%22%2C%22%3F%22%2C%22%3F%22%2C9.2%29%29


I only did one number in the final answer, the 23, which became 9.2
after we multiplied everything in the matrix by 0.4.  Notice it was 
in the 3rd row and the 2nd column.

So I took the elements of the 3rd row from the first matrix,
which are 3 and 5.  Then I multiplied them by the elements
of the 3rd column which are 1 and 4, that is I calculated
this:

3×1+5×4 = 3+20 = 23. Then for the final answer we multiply each
number by the 0.4 and when we multiply the 23 by 0.4 we get 9.2.

You calculate the other 5 numbers where the question marks are.

Edwin