The most underrated math theorem but Google secretly used it to change the world. Perron-Frobenius Theorem (positive matrix version): Let A be an n×n matrix with every entry a_{ij} > 0. Then there exists a unique positive real number λ > 0 (the Perron root) and a unique (up to scaling) positive vector x > 0 such that: A x = λ x Moreover: λ = ρ(A) (spectral radius of A) λ > |μ| for every other eigenvalue μ λ is simple (algebraic multiplicity = 1) Your search results aren't just a list; they are the coordinates of a high-dimensional vector pointing toward the most authoritative nodes on the web.