A collection of covariation applets.
A possible way to work with each of them is to
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[*] ask students to try dragging each point in the applet, to check which points can be moved and then to say how the other points then move in relation to the point being moved by them,
[*] ask students to work together in pairs, then share solutions as in a larger group, and then write three different solutions (for how the points move in relation to each other) and to give reasons for one solution to be their favorite
[*] then ask students to recreate the applet themselves in GeoGebra.
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It is possible to work with these tasks with or without attention to coordinates.
A more detailed description of how one class worked on the first task is found in the paper:
Gíslason, I. (2021). Discussing Dependencies of Variable Points on the Basis of a GeoGebra Task: Meaning Making in a Teacher-Class Dialogue. Digital Experiences in Mathematics Education, 7(2), 301–322. https://doi.org/10.1007/s40751-021-00087-7