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Question 35199: Show that AB = BA is not true in general for matrix multiplication, by offering a coun-terexample with matrices A and B of the same size. Give your own matrices.
So is the following in example
I used
A=|2,4|and
B=|2|
.....|4|
|2,4|*|2|
.........|4|
is not = to
|2|*|2,4|
|4|
have I got it right?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! No. Your 1st product can be calculated; it is a 1X1 matrix [2*2+4*4]=[18]
But your 2nd product cannot be calculated since the number of rows of A
do not equal the number of columns of B. It is not a counter example.
Try a 2X2 matrix with entries 1,2,3,4
multiplying another 2X2 matrix with entries 4,3,2,1.
Numbers in the products will be the same but the
matrices will not be equal.
That should work
Cheers,
Stan H.
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