CS 229 - Linear Algebra and Calculus refresher

Remark: the vector $x$ defined above can be viewed as a $n\times1$ matrix and is more particularly called a column-vector. Remark: for matrices $A,B$, we have $(AB) T B TA T$. Remark: not all square matrices are invertible. Remark: $A$ is invertible if and only if $ A eq0$. Linearly dependence A set of vectors is said to be linearly dependent if one of the vectors in the set can be defined as a linear combination of the others.