CAIE FP1 2013 November — Question 7 9 marks

Exam BoardCAIE
ModuleFP1 (Further Pure Mathematics 1)
Year2013
SessionNovember
Marks9
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicIntegration with Partial Fractions
TypeRational function curve sketching
DifficultyStandard +0.8 This Further Maths question requires polynomial division to find oblique asymptote, differentiation of a quotient (or rewritten form), proving an inequality involving the derivative for all x in the domain, and synthesizing all information into an accurate sketch. While individual techniques are standard, the combination of algebraic manipulation, calculus, and curve sketching with multiple features (vertical and oblique asymptotes, gradient constraint) makes this moderately challenging.
Spec1.02n Sketch curves: simple equations including polynomials1.02y Partial fractions: decompose rational functions1.07n Stationary points: find maxima, minima using derivatives

7 The curve \(C\) has equation $$y = \frac { 2 x ^ { 2 } + 5 x - 1 } { x + 2 }$$ Find the equations of the asymptotes of \(C\). Show that \(\frac { \mathrm { d } y } { \mathrm {~d} x } > 2\) at all points on \(C\). Sketch C.

Question 7:
AnswerMarks Guidance
Working/AnswerMarks Guidance
Vertical asymptote is \(x = -2\)B1
\(y = 2x + 1 - 3(x+2)^{-1}\)M1 Expresses \(y\) in suitable form
Oblique asymptote is \(y = 2x+1\)A1 (3)
\(y' = 2 + 3(x+2)^{-2}\)M1A1 Differentiates wrt \(x\)
\((x+2)^{-2} > 0 \Rightarrow y' > 2\)A1 (3) AG
Axes and asymptotesB1 Sketches graph
Each branch, showing intersection with axesB1B1 (3) Deduct 1 mark for poor forms at infinity
Total: [9]
## Question 7:

| Working/Answer | Marks | Guidance |
|---|---|---|
| Vertical asymptote is $x = -2$ | B1 | |
| $y = 2x + 1 - 3(x+2)^{-1}$ | M1 | Expresses $y$ in suitable form |
| Oblique asymptote is $y = 2x+1$ | A1 | **(3)** |
| $y' = 2 + 3(x+2)^{-2}$ | M1A1 | Differentiates wrt $x$ |
| $(x+2)^{-2} > 0 \Rightarrow y' > 2$ | A1 | **(3)** AG |
| Axes and asymptotes | B1 | Sketches graph |
| Each branch, showing intersection with axes | B1B1 | **(3)** Deduct 1 mark for poor forms at infinity |

**Total: [9]**
7 The curve $C$ has equation

$$y = \frac { 2 x ^ { 2 } + 5 x - 1 } { x + 2 }$$

Find the equations of the asymptotes of $C$.

Show that $\frac { \mathrm { d } y } { \mathrm {~d} x } > 2$ at all points on $C$.

Sketch C.

\hfill \mbox{\textit{CAIE FP1 2013 Q7 [9]}}