This lecture covers the concepts of translations and homotheties, explaining how a vector's translation is a geometric transformation described by M² = t_(M), and how homotheties are transformations described by M² = h_₂₁ α (M) = t₁² (2²). It also delves into the analytical expressions of these transformations, showing how to describe them using coordinates. The lecture concludes with a discussion on the stability of homotheties/translations by composition.