free math books - SERP Analysis

https://open.umn.edu/opentextbooks/subjects/mathematics

https://bim.easyaccessmaterials.com/

https://freecomputerbooks.com/mathCategory.html

https://openstax.org/subjects/math

https://www.reddit.com/r/learnmath/comments/gxu53c/free_pdf_textbooks/

https://www.openculture.com/free-math-textbooks

https://www.sciencebooksonline.info/mathematics.html

https://www.freecodecamp.org/news/free-textbooks-math-science-and-more-online-pdf-for-college-and-high-school/

https://archive.org/details/math_book

https://textbooks.aimath.org/