Here is a simple set of slides created using Geogebra. I would normally just do this directly on Geogebra but as I needed to prepare some slides for our department planning, I thought I would share them. I have added some suggestions for how to run these in the notes section
I want students to make the connection that if the y-value doesn’t change for a bunch of coordinates (in this base the y-value is always 4) then the line that those coordinates all sit on is y=4. I’ve even made a little GIF where the point deliberately slides off the the right for a little while. Gotta love a GIF!