I'm not sure about the objective of this question

I'm not sure about what the objective of the question. I assume that the polynomial coefficient vector means that I should do something like ployfit(x, y)?

[Torsten]

Yes, polyfit and polyval.

[Sherman Ng]

OK so I tried to do polyval(polyfit(x, y, 9), x) but apparently it's not right, any other tips?

[Torsten]

Yes, my tip is to study the first example under

https://de.mathworks.com/help/matlab/ref/polyfit.html