OCR MEI C2 — Question 9 3 marks

Exam BoardOCR MEI
ModuleC2 (Core Mathematics 2)
Marks3
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicStationary points and optimisation
TypeFind range where function increasing/decreasing
DifficultyModerate -0.5 This is a straightforward application of differentiation to find increasing intervals. Students need to find f'(x) = 12 - 3x², set f'(x) > 0, and solve the quadratic inequality. While it requires multiple steps, it's a standard C2 technique with no conceptual surprises, making it slightly easier than average.
Spec1.07o Increasing/decreasing: functions using sign of dy/dx
9 Use calculus to find the set of values of \(x\) for which \(\mathrm { f } ( x ) = 12 x - x ^ { 3 }\) is an increasing function.
Question 9:
AnswerMarks Guidance
\([f'(x) =]\ 12 - 3x^2\)B1
their \(f'(x) > 0\) or \(= 0\) soiM1
\(-2 < x < 2\)A1 condone \(-2 \leq x \leq 2\) or "between \(-2\) and \(2\)" 
## Question 9:

$[f'(x) =]\ 12 - 3x^2$ | B1 |
their $f'(x) > 0$ or $= 0$ soi | M1 |
$-2 < x < 2$ | A1 | condone $-2 \leq x \leq 2$ or "between $-2$ and $2$" | 3

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9 Use calculus to find the set of values of $x$ for which $\mathrm { f } ( x ) = 12 x - x ^ { 3 }$ is an increasing function.

\hfill \mbox{\textit{OCR MEI C2  Q9 [3]}}
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