Here is a YouTube video about Least Squares Using Matrices as Matrix Algebra, and is part of a growing collection of videos I have found to be useful. The reason is working out the least-squares problem for fitting a line through noisy data and understanding science related to software defined radio.
This tutorial, "Least Squares Using Matrices as Matrix Algebra" is free education you can watch, which will help you deepen your knowledge and be better prepared for licence exams, schoolwork, or operating radio equipment.