OCR MEI C3 — Question 6 3 marks

Exam BoardOCR MEI
ModuleC3 (Core Mathematics 3)
Marks3
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicComposite & Inverse Functions
TypeTransformations of functions
DifficultyModerate -0.8 This question requires finding a composite function fg(x) = f(g(x)) = ln(x³) = 3ln(x), which is straightforward substitution and use of log laws. Identifying the transformation (vertical stretch scale factor 3) is also routine. This is simpler than a typical C3 question as it involves only basic composition and a single standard transformation with no inverse functions or complex multi-step work.
Spec1.02v Inverse and composite functions: graphs and conditions for existence1.02w Graph transformations: simple transformations of f(x)1.06d Natural logarithm: ln(x) function and properties

6 The functions \(\mathrm { f } ( x )\) and \(\mathrm { g } ( x )\) are defined for the domain \(x > 0\) as follows: $$\mathrm { f } ( x ) = \ln x , \quad \mathrm {~g} ( x ) = x ^ { 3 } .$$ Express the composite function \(\mathrm { fg } ( x )\) in terms of \(\ln x\).
State the transformation which maps the curve \(y = \mathrm { f } ( x )\) onto the curve \(y = \mathrm { fg } ( x )\).

Question 6:
AnswerMarks Guidance
\(fg(x) = \ln(x^3) = 3\ln x\)M1, A1 \(\ln(x^3) = 3\ln x\)
Stretch scale factor 3 in \(y\) directionB1
## Question 6:

| $fg(x) = \ln(x^3) = 3\ln x$ | M1, A1 | $\ln(x^3) = 3\ln x$ |
|---|---|---|
| Stretch scale factor 3 in $y$ direction | B1 | |

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6 The functions $\mathrm { f } ( x )$ and $\mathrm { g } ( x )$ are defined for the domain $x > 0$ as follows:

$$\mathrm { f } ( x ) = \ln x , \quad \mathrm {~g} ( x ) = x ^ { 3 } .$$

Express the composite function $\mathrm { fg } ( x )$ in terms of $\ln x$.\\
State the transformation which maps the curve $y = \mathrm { f } ( x )$ onto the curve $y = \mathrm { fg } ( x )$.

\hfill \mbox{\textit{OCR MEI C3  Q6 [3]}}