- #1
Saladsamurai
- 3,020
- 7
Homework Statement
Show that (AB)C=A(BC)
I am just trying to do this to try to gain some experience with problems like this. I saw in my text that they did a similar example for distributivity using the definition of matrix multiplication, so I thought I could use that approach.
The Attempt at a Solution
Let the (i,j)-entry of A be given by aij
Let the (i,j)-entry of B be given by bij
Let the (i,j)-entry of C be given by cij
Then the (i,j)-entry of (AB) is given by
[tex]\sum_{k=1}^na_{ik}b_{kj}[/tex]
Here is where I get lost. I was thinking of then writing that the (i,j)-entry of (AB)C would be given by
[tex]\sum_{k=1}^n(a_{ik}b_{kj})c_{kj}[/tex]but I don't think that this works...and I am not sure why or why not
Any hints?
Thanks!