1.2.1. Funcții, lecturi grafice - clasa a IX-a, 1.2.2. Funcția de gradul I - clasa a IX-a
https://www.edumo.org/capitol/5318862266433536
Functia de gradul I,
https://www.edumo.org/capitol/5907959712317440
https://www.edumo.org/capitol/5275240028438528
https://matematic.eu/Clasa9/FunctiaDeGrad1.pdf
https://matematic.eu/Teorie_probleme/FuncitiaDeGradul1Bac2011-2016.pdf