WebsiteintermediateFree
ocw.mit.edu
Unknown
MIT OpenCourseWare (OCW) provides free, MIT-published course materials; for matrices, you can explore linear algebra courses with lecture notes, problem sets, exams, and video lectures covering matrices and related concepts.
More resources on Matrices
WebsiteFree
Paul's Online Math Notes - Linear Algebra
Detailed notes on matrices, free textbook style
WebsiteFree
3Blue1Brown Linear Algebra Series
Animated visualizations for matrices and transformations
WebsiteFree
MIT OpenCourseWare Linear Algebra
Full course with videos, notes, exams
VideoFree
Eigenvectors and eigenvalues | Essence of linear algebra
Intuitive explanation of eigenvalues
VideoFree
The Matrix Equation Ax=b
Gilbert Strang lecture on solving systems with matrices
VideoFree
Essence of Linear Algebra Chapter 1: Vectors
Visual introduction to vectors, column space, null space