Source: https://www.cesstex.be/institut-sainte-therese/infos-aux-eleves-et-aux-parents/documents-utiles/covid-2022-annee-scolaire-2020-21/279c-manage/m-5emes/m-5-vente/M_5%20P%20VENTE_MATH_%20Chapitre%201_%20Fonctions%201er%20degre%20.pdf