The aim of this research is to advance in the teaching-learning process of representing quadratic functions, both with pencil and paper and with a technological tool. For this purpose, a didactic experience is presented. Firstly, it is explained in the traditional way how to graph a quadratic function; secondly, students are introduced to the GeoGebra software. It provides a categorization of the different errors and difficulties of the students, the comparison between a graphic representation with paper and pencil and a representation with GeoGebra, and the improvement with the technological tool.