AQA FP1 2009 January — Question 7 10 marks

Exam BoardAQA
ModuleFP1 (Further Pure Mathematics 1)
Year2009
SessionJanuary
Marks10
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicStraight Lines & Coordinate Geometry
TypeLine and curve intersection
DifficultyStandard +0.3 Part (a) is a straightforward coordinate geometry derivation using the two-point form of a line and finding x-intercept. Parts (b)(i-ii) involve substituting into a quartic, solving equations, and numerical approximation. While it spans multiple steps, each component uses standard A-level techniques without requiring novel insight—slightly easier than average due to the guided structure.
Spec1.03a Straight lines: equation forms y=mx+c, ax+by+c=0

7 The points \(P ( a , c )\) and \(Q ( b , d )\) lie on the curve with equation \(y = \mathrm { f } ( x )\). The straight line \(P Q\) intersects the \(x\)-axis at the point \(R ( r , 0 )\). The curve \(y = \mathrm { f } ( x )\) intersects the \(x\)-axis at the point \(S ( \beta , 0 )\). \includegraphics[max width=\textwidth, alt={}, center]{38c2a2c8-84cc-4bd2-b3ad-f9dee59763ba-4_951_971_470_539}
  1. Show that $$r = a + c \left( \frac { b - a } { c - d } \right)$$
  2. Given that $$a = 2 , b = 3 \text { and } \mathrm { f } ( x ) = 20 x - x ^ { 4 }$$
    1. find the value of \(r\);
    2. show that \(\beta - r \approx 0.18\).

Question 7(a):
AnswerMarks Guidance
Answer/WorkingMarks Guidance
Use of similar triangles or algebraM1 Some progress needed
Correct relationship establishedm1A1 e.g. \(\dfrac{r-a}{c} = \dfrac{b-a}{c-d}\)
Hence result convincingly shownA1 AG
Total4
Question 7(b)(i):
AnswerMarks Guidance
Answer/WorkingMarks Guidance
\(c = f(a) = 24\), \(d = f(b) = -21\)B1, B1
\(r = \dfrac{38}{15}\ (\approx 2.5333)\)B1F Allow AWRT 2.53; ft small error
Total3
Question 7(b)(ii):
AnswerMarks Guidance
Answer/WorkingMarks Guidance
\(\beta = 20^{\frac{1}{3}} \approx 2.714(4)\)M1A1 Allow AWRT 2.71
So \(\beta - r \approx 0.181 \approx 0.18\) (AG)A1 Allow only 2dp if earlier values to 3dp
Total10
## Question 7(a):

| Answer/Working | Marks | Guidance |
|---|---|---|
| Use of similar triangles or algebra | M1 | Some progress needed |
| Correct relationship established | m1A1 | e.g. $\dfrac{r-a}{c} = \dfrac{b-a}{c-d}$ |
| Hence result convincingly shown | A1 | AG |
| **Total** | **4** | |

## Question 7(b)(i):

| Answer/Working | Marks | Guidance |
|---|---|---|
| $c = f(a) = 24$, $d = f(b) = -21$ | B1, B1 | |
| $r = \dfrac{38}{15}\ (\approx 2.5333)$ | B1F | Allow AWRT 2.53; ft small error |
| **Total** | **3** | |

## Question 7(b)(ii):

| Answer/Working | Marks | Guidance |
|---|---|---|
| $\beta = 20^{\frac{1}{3}} \approx 2.714(4)$ | M1A1 | Allow AWRT 2.71 |
| So $\beta - r \approx 0.181 \approx 0.18$ (AG) | A1 | Allow only 2dp if earlier values to 3dp |
| **Total** | **10** | |

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7 The points $P ( a , c )$ and $Q ( b , d )$ lie on the curve with equation $y = \mathrm { f } ( x )$. The straight line $P Q$ intersects the $x$-axis at the point $R ( r , 0 )$. The curve $y = \mathrm { f } ( x )$ intersects the $x$-axis at the point $S ( \beta , 0 )$.\\
\includegraphics[max width=\textwidth, alt={}, center]{38c2a2c8-84cc-4bd2-b3ad-f9dee59763ba-4_951_971_470_539}
\begin{enumerate}[label=(\alph*)]
\item Show that

$$r = a + c \left( \frac { b - a } { c - d } \right)$$
\item Given that

$$a = 2 , b = 3 \text { and } \mathrm { f } ( x ) = 20 x - x ^ { 4 }$$
\begin{enumerate}[label=(\roman*)]
\item find the value of $r$;
\item show that $\beta - r \approx 0.18$.
\end{enumerate}\end{enumerate}

\hfill \mbox{\textit{AQA FP1 2009 Q7 [10]}}