Yes, that is a leftover reference to a static image from a prior WeBWorK/GeoGebra problem that I used as a foundation for helping you with your question.
I've now updated this code to dynamically generate an image for each randomization via the AskSage functionality of WeBWorK. (This was actually my first attempt at using AskSage in WeBWorK, so thank you for the inspiration )
The code is attached here, but essentially the additions include querying Sage (to do what GeoGebra is also doing - ugh, redundancy) but I don't know how to retrieve the fitted polynomial from GeoGebra before the problem has even been attempted. So instead, Sage and some Python are used to retrieve (and reasonably format) our polynomial. That polynomial is then added to an image (for hardcopy), and its derivative is added to a second image that is displayed in the solution.
Let me know if you have any questions about the code, I'd be happy to clarify wherever necessary.