2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/78557We present a theory of reduction of binary quadratic forms with coefficients in Z[lambda], where lambda is the minimal translation in a Hecke group. We generalize from the modular group Gamma(1) = SL(2,Z) to the Hecke groups and make extensive use of modified negative continued fractions.17 pages. See also http://www.fandm.edu/people/w_ressler Changes from v. 2: I dispensed with the incorrect Lemma 5 and replaced the incorrect Lemma 8 with a true Theorem 1, which characterizes reduced numbers for the Hecke groupsNumber Theory11H55 (primary); 11F06,11J70 (secondary)text