M1 Attempts to use f′(3)=2⇒2=9+3a+b oe. The expression does not need to be simplified so embedded values scores this mark. Condone slips when squaring but do not allow f′(3)=−2
M1 Attempts to integrate and achieves (f(x)=)…x3+…ax2+bx+(c) with or without the +c.a,b=0
dM1 Uses y intercept =-8 and (3,-2) in their (f(x)=)…x3+…ax2+bx+c. The values embedded in the expression are sufficient. It is dependent on the previous method mark only.
Alternatively uses (3,-2) in (f(x)=)…x3+…ax2+bx−8
Beware: they may also substitute in b=-7-3 a at some point to achieve an equation in a only.
A1 Correct unsimplified equation in a and b−2=9+29a+3b−8.
Note: simplified becomes 9 a+6 b=-6
Alternatively they may have a correct unsimplified equation in a only: −2=9+29a+3(−7−3a)−8 oe eg 4.5 a=-18
ddM1 Dependent upon all previous M's.
It is for solving their two equations with c=-8 to find values for a and b or solving their equation in a and then substituting in to b=-7-3 a to find a value for b
Don't be too concerned by the process. A calculator method is acceptable.
A1 31x3−2x2+5x−8 as their final answer. Do not isw eg 31x3−2x2+5x−8→x3−6x2+15x−24y=… or f(x)=… are not required. Do not allow 5x1.