CAIE P1 2022 November — Question 9 8 marks

Exam BoardCAIE
ModuleP1 (Pure Mathematics 1)
Year2022
SessionNovember
Marks8
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicFunction Transformations
TypeExpress function using transformations
DifficultyModerate -0.8 This is a routine completing-the-square question with standard transformations. Parts (a) and (b) are textbook exercises requiring only algebraic manipulation. Part (c) requires connecting the two forms but follows directly from the previous work. Part (d) tests basic understanding of function transformations (stretch and translation), which is standard P1 content with no problem-solving insight needed.
Spec1.02e Complete the square: quadratic polynomials and turning points1.02w Graph transformations: simple transformations of f(x)

9 Functions f and g are both defined for \(x \in \mathbb { R }\) and are given by $$\begin{aligned} & \mathrm { f } ( x ) = x ^ { 2 } - 4 x + 9 \\ & \mathrm {~g} ( x ) = 2 x ^ { 2 } + 4 x + 12 \end{aligned}$$
  1. Express \(\mathrm { f } ( x )\) in the form \(( x - a ) ^ { 2 } + b\).
  2. Express \(\mathrm { g } ( x )\) in the form \(2 \left[ ( x + c ) ^ { 2 } + d \right]\).
  3. Express \(\mathrm { g } ( x )\) in the form \(k \mathrm { f } ( x + h )\), where \(k\) and \(h\) are integers.
  4. Describe fully the two transformations that have been combined to transform the graph of \(y = \mathrm { f } ( x )\) to the graph of \(y = \mathrm { g } ( x )\).

Question 9:
Part 9(a):
AnswerMarks
\((x-2)^2 + 5\)B1
Part 9(b):
AnswerMarks
\(2\left(\left\{(x+1)^2\right\} + \{5\}\right)\)B2, 1, 0
Part 9(c):
AnswerMarks Guidance
\([g(x) =]\ 2f(x+3)\) or \(k=2,\ h=3\)B1 In correct form. B0 if contradiction
Part 9(d):
AnswerMarks Guidance
Translation \(\begin{pmatrix}-3\\0\end{pmatrix}\)B2, 1, 0 FT FT on *their* \(x+3\) or \(h=3\)
Stretch \(\{y\) direction, factor \(2\}\)B2, 1, 0 FT FT on *their* \(2\) or \(k=2\)
## Question 9:

### Part 9(a):

| $(x-2)^2 + 5$ | B1 | |
|---|---|---|

### Part 9(b):

| $2\left(\left\{(x+1)^2\right\} + \{5\}\right)$ | B2, 1, 0 | |
|---|---|---|

### Part 9(c):

| $[g(x) =]\ 2f(x+3)$ or $k=2,\ h=3$ | B1 | In correct form. B0 if contradiction |
|---|---|---|

### Part 9(d):

| Translation $\begin{pmatrix}-3\\0\end{pmatrix}$ | B2, 1, 0 FT | FT on *their* $x+3$ or $h=3$ |
|---|---|---|
| Stretch $\{y$ direction, factor $2\}$ | B2, 1, 0 FT | FT on *their* $2$ or $k=2$ |

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9 Functions f and g are both defined for $x \in \mathbb { R }$ and are given by

$$\begin{aligned}
& \mathrm { f } ( x ) = x ^ { 2 } - 4 x + 9 \\
& \mathrm {~g} ( x ) = 2 x ^ { 2 } + 4 x + 12
\end{aligned}$$
\begin{enumerate}[label=(\alph*)]
\item Express $\mathrm { f } ( x )$ in the form $( x - a ) ^ { 2 } + b$.
\item Express $\mathrm { g } ( x )$ in the form $2 \left[ ( x + c ) ^ { 2 } + d \right]$.
\item Express $\mathrm { g } ( x )$ in the form $k \mathrm { f } ( x + h )$, where $k$ and $h$ are integers.
\item Describe fully the two transformations that have been combined to transform the graph of $y = \mathrm { f } ( x )$ to the graph of $y = \mathrm { g } ( x )$.
\end{enumerate}

\hfill \mbox{\textit{CAIE P1 2022 Q9 [8]}}