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.

also I realised there's no c bc it crosses (0,0)

(edited 11 months ago)

Reply 1

esha06

Original post by esha06

Reply 2

mqb2766

Original post by esha06

The third item says (2,9) is a stationary point.

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

(edited 11 months ago)

Reply 3

esha06

Original post by mqb2766

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

(edited 11 months ago)

Reply 4

mqb2766

Original post by esha06

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.

Reply 5

esha06

Original post by mqb2766

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

Reply 6

mqb2766

Original post by esha06

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

youve already used that point to get c=0. You are told for this point that
9 = g(2)
0 = g'(2)
so two simultaneous equations in two parameters.

Its really worth writing each point down mathematically like this.

As per a previous thread, can you try giving a more meaningful title.