CAIE FP1 2015 November — Question 8 11 marks

Exam BoardCAIE
ModuleFP1 (Further Pure Mathematics 1)
Year2015
SessionNovember
Marks11
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicIntegration with Partial Fractions
TypeRational function curve sketching
DifficultyStandard +0.8 This is a Further Maths question requiring implicit differentiation of a rational function using the quotient rule, solving an inequality involving a discriminant (no stationary points means dy/dx ≠ 0), then analyzing asymptotes (vertical, oblique via polynomial division) and sketching. The multi-step nature, discriminant analysis, and oblique asymptote identification elevate this above standard C3/C4 calculus questions, though it follows established techniques without requiring novel insight.
Spec1.02n Sketch curves: simple equations including polynomials1.07m Tangents and normals: gradient and equations1.07n Stationary points: find maxima, minima using derivatives

The curve \(C\) has equation \(y = \frac{2x^2 + kx}{x + 1}\), where \(k\) is a constant. Find the set of values of \(k\) for which \(C\) has no stationary points. [5] For the case \(k = 4\), find the equations of the asymptotes of \(C\) and sketch \(C\), indicating the coordinates of the points where \(C\) intersects the coordinate axes. [6]

Question 8:
AnswerMarks
8( )
y′=0⇒(x+1)(4x+k)− 2x2+kx ×1=0
⇒4x2+(4+k)x+k−2x2−kx=0⇒2x2+4x+k =0
B2 −4AC<0⇒ no stationary points ⇒16−8k <0
⇒ k > 2 for no stationary points.
When k = 4:
Vertical asymptote: x = –1
2
Oblique asymptote: y=2x+2− ⇒ y = 2x + 2
x+1
Axes and asymptotes
AnswerMarks
Each branch.M1
A1
M1A1
A1
[5]
B1
M1A1
B1
B1B1
[6]

Total

11
AnswerMarks Guidance
Page 7Mark Scheme Syllabus
Cambridge International A Level – October/November 20159231 11
Qn &
AnswerMarks Guidance
PartSolution Marks
Question 8:
8 | ( )
y′=0⇒(x+1)(4x+k)− 2x2+kx ×1=0
⇒4x2+(4+k)x+k−2x2−kx=0⇒2x2+4x+k =0
B2 −4AC<0⇒ no stationary points ⇒16−8k <0
⇒ k > 2 for no stationary points.
When k = 4:
Vertical asymptote: x = –1
2
Oblique asymptote: y=2x+2− ⇒ y = 2x + 2
x+1
Axes and asymptotes
Each branch. | M1
A1
M1A1
A1
[5]
B1
M1A1
B1
B1B1
[6]
Total
11
Page 7 | Mark Scheme | Syllabus | Paper
Cambridge International A Level – October/November 2015 | 9231 | 11
Qn &
Part | Solution | Marks
The curve $C$ has equation $y = \frac{2x^2 + kx}{x + 1}$, where $k$ is a constant. Find the set of values of $k$ for which $C$ has no stationary points. [5]

For the case $k = 4$, find the equations of the asymptotes of $C$ and sketch $C$, indicating the coordinates of the points where $C$ intersects the coordinate axes. [6]

\hfill \mbox{\textit{CAIE FP1 2015 Q8 [11]}}