Mathematics
Polynomial Roots and the Fundamental Theorem of Algebra
Quick fact
The Fundamental Theorem of Algebra was first proven by Carl Friedrich Gauss in 1799, and it guarantees that every polynomial of degree n has exactly n complex roots (counting multiplicity).
Why this is interesting
You know that a quadratic can have two, one, or zero real solutions—but what if you were told that it always has exactly two solutions? The catch is that some are hidden in a world beyond real numbers.