In this article we present a didactic proposal for teaching linear algebra based on two compatible theoretical models: emergent models and mathematical modelling. This proposal begins with a problematic situation related to the creation and use of secure passwords, which leads students toward the construction of the concepts of spanning set and span. The objective is to evaluate this didactic proposal by determining the level of match between the hypothetical learning trajectory (HLT) designed in this study with the actual learning trajectory in the second experimental cycle of an investigation design-based research more extensive. The results show a high level of match between the trajectories in more than half of the conjectures, which gives evidence that the HLT has supported, in many cases, the achievement of the learning objective, and that additionally mathematical modelling contributes to the construction of these linear algebra concepts.

A continuing challenge in mathematics education at the university level is how to create learning environments that give students the opportunity to progress fromtheir informal ways of reasoning to more formal ways of reasoning. This article shows how the emergent models heuristic (Gravemeijer, 1999, Math. Think. Learn, 1, 155-177) provides this opportunity to first-year university students, specifically for them to construct the Linear Algebra concepts of spanning set and span. For this, a design-based research methodology was used. A hypothetical learning trajectory (HLT) was applied, created within the framework of this heuristic. The results provide evidence that the emergent models heuristic support the construction of these concepts of Linear Algebra. Moreover, useful tips are given for using this heuristic to construct mathematical concepts.