A level Maths OCR question help

for this question i realised that bc it was cubic the function would be something like ax^3+bx^2+ax +c ( 2 a's bc it says they're the same in the question) but then I don't really know where to go from there. maybe differentiate and substitute (2,9)?

The second item says the origin (0,0) lies on the curve
The third item says (2,9) is a stationary point.

So you should have enough to get the three coefficients a, b and c. Write each item out clearly in terms of the cubic (and its derivative).

i did that but idk what to do with the coordinate

also I just realised the last x should be a

So you have two "points" in terms of two unknowns a, b so solve simultaneously.

but if i substitute (0,0) into g(x) ill get get 0