Disappearing lines

I have an activity where the tangent line shows up in the editing mode, but not in the student preview mode, nor in the actual student activity. Any ideas?

The code I use for the tangent line in Screen 3 is the same I use in 1 and 2, and the lines show up in the student views there.

Difference between screens 1 and 2 and screen 3 is the table.

Looks like you created a new number y_1 thats overriding any other y_1 in the graph. That includes your tangent line
If you name it something else in the graph you should be good to go.

Pro tip: if its just for a visual you don’t actually need y= in this case. OOoooh and you can use F’(a) to save you a line and some work! Desmos | Graphing Calculator

Thank you for the tips.