French mathematician Évariste Galois died #OTD in 1832.
Galois developed a deep understanding of the relationship between polynomial equations and group theory. He showed how the solutions to polynomial equations are related to the structure of certain groups, now called Galois groups. This connection helps determine whether a polynomial can be solved by radicals (i.e., using a finite number of root extractions).
Galois at PG:
https://www.gutenberg.org/ebooks/author/40484