Math / Building Blocks
Many Numbers at Once
Linear algebra handles many numbers at once. A vector is a list of numbers with a direction and a size; a matrix is a transformation that moves every vector in the same consistent way; solving a system of equations asks which input a transformation sends to a given output. Most of data science, computer graphics, and machine learning is linear algebra wearing different clothes.
Linear Algebra Essentials
See it first
3Blue1Brown's visual series builds the intuition before the arithmetic.
3b1b: essence of linear algebraThe classic course
Gilbert Strang's MIT lectures, free with problem sets.
mit ocw: 18.06Interactive textbook
Figures you can drag while you read.
immersive linear algebraParallel and Competing Theories
The European names on these methods came late. Solving many equations at once was worked out in China first.
The Nine Chapters
The Nine Chapters on the Mathematical Art, compiled in China by around the first century CE, solves systems of linear equations by arranging coefficients in a grid and eliminating, the method later named for Gauss.
wiki: The Nine Chapters