So far, we've learned how to add and subtract matrices (the sizes had to be the same) and how to multiply a matrix by a scalar. These were really easy.
Multiplying two matrices is a bit tricky, but, once you get the hang of it, it's a snap -- you just need to be careful!
First of all, the size of the two matrices you are multiplying is super important!
Here's how it works:
Say the size of matrix A is 3 x 4
and the size of matrix B is 4 x 1
and we want ...
Looking at the sizes...
You'll see this when we do one.
If the size of matrix A is m x n
and the size of matrix B is n x p,
This is for ...
Can we multiply ? No!
For this to all make sense, we really just need to do one.