It would be nice to re-iterate what we are trying to calculate - I was stuck for a long time calculating f(x) whereas I needed to calculate the first derivative f'(x).

Consider rephrasing this line: "Your function will receive 2 arguments: a polynomial as a string, and a point to evaluate the equation as an integer." as
"Your function will receive 2 arguments: a polynomial as a string, and a value of 'x' as an integer. It should return the first derivative of the polynomial at the given point x".

I hope this isn't a spoiler.