What is the mysterious axiom of choice? Why the hell do we need it even just to show that every infinite set has a countable subset? Why does every vector space have a basis? ...

The best approximate solution to a system of linear equations, and applications beyond linear equations.

This post is part of a series of algorithm notes originally intended only for myself.

This post is part of a series of algorithm notes originally intended only for myself.

The awkward introduction and definition of determinants often puzzle beginners, including me. However, as the level of abstraction increases, its motivation becomes clearer and the underlying elegance emerges.