2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/115615The fundamental unit of $\Z[\sqrt{N}]$ for square-free $N=5 mod 8$ is either $ε$ or $ε^3$ where $ε$ denotes the fundamental unit of the maximal order of $\Q(\sqrt{N})$. We give infinitely many examples for each case.4 pagesNumber Theory11R65;11R29text