Matrix Multiplication
## Formula
If $$a$$ is of order $m\times n$ and $$b$$ is of order $n\times p$, then:
$$AB=C$$
where $$c$$ is of order:
$$m\times p$$
and:
$$c_{ij}=\sum_{k=1}^{n}a_{ik}b_{kj}$$
## Condition
The number of columns of $$a$$ must equal the number of rows of $$b$$.
## Usage
- Used to multiply matrices and represent systems of linear transformations.