Niels Henrik Abel
The life of Niels Henrik Abel - The Starving Genius Who Rewrote Algebra
Abel's Impossibility Theorem
Proving there is no general formula in radicals for the roots of quintic equations.
\[ a_5 x^5 + a_4 x^4 + a_3 x^3 + a_2 x^2 + a_1 x + a_0 = 0 \]
Sources: https://mathshistory.st-andrews.ac.uk/Biographies/Abel/
