OCR FP2 2006 June — Question 3 6 marks

Exam BoardOCR
ModuleFP2 (Further Pure Mathematics 2)
Year2006
SessionJune
Marks6
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicComposite & Inverse Functions
TypeState domain or range
DifficultyStandard +0.8 This FP2 question requires finding an asymptote (straightforward) and proving range bounds using calculus or completing the square. The inequality proof demands algebraic manipulation and critical point analysis, going beyond routine exercises but using standard A-level techniques.
Spec1.02k Simplify rational expressions: factorising, cancelling, algebraic division1.02n Sketch curves: simple equations including polynomials1.07n Stationary points: find maxima, minima using derivatives

3 The equation of a curve is \(y = \frac { x + 1 } { x ^ { 2 } + 3 }\).
  1. State the equation of the asymptote of the curve.
  2. Show that \(- \frac { 1 } { 6 } \leqslant y \leqslant \frac { 1 } { 2 }\).

AnswerMarks Guidance
(i) State \(y = 0\) (or seen if working given)B1 Must be \(=\); accept \(x\)-axis; ignore any others
(ii) Write as quad. in \(x^2\)M1 \((x^2 - x + (3y-1) = 0)\)
Use for real \(x\), \(b^2-4ac \geq 0\)M1 Allow \(>\) ; or \(<\) for no real \(x\)
Produce quad. inequality in \(y\)M1 \(1 \leq 12y^2 - 4y ; 12y^2 - 4y - 1 \leq 0\)
Attempt to solve inequalityM1 Factorise/ quadratic formula
Justify A.G.A1 e.g. diagram / table of values of \(y\)
SCAttempt diff. by product/quotient M1
Solve \(\frac{dy}{dx} = 0\) for two real \(x\)M1
Get both \((-3, -\frac{\sqrt{6}}{8})\) and \((1, \frac{1}{2})\)A1
Clearly prove min./max.A1
Justify fully the inequality e.g. detailed graphB1
**(i)** State $y = 0$ (or seen if working given) | B1 | Must be $=$; accept $x$-axis; ignore any others

**(ii)** Write as quad. in $x^2$ | M1 | $(x^2 - x + (3y-1) = 0)$
Use for real $x$, $b^2-4ac \geq 0$ | M1 | Allow $>$ ; or $<$ for no real $x$
Produce quad. inequality in $y$ | M1 | $1 \leq 12y^2 - 4y ; 12y^2 - 4y - 1 \leq 0$
Attempt to solve inequality | M1 | Factorise/ quadratic formula
Justify A.G. | A1 | e.g. diagram / table of values of $y$
| SC | Attempt diff. by product/quotient | M1
| | Solve $\frac{dy}{dx} = 0$ for two real $x$ | M1
| | Get both $(-3, -\frac{\sqrt{6}}{8})$ and $(1, \frac{1}{2})$ | A1
| | Clearly prove min./max. | A1
| | Justify fully the inequality e.g. detailed graph | B1
3 The equation of a curve is $y = \frac { x + 1 } { x ^ { 2 } + 3 }$.\\
(i) State the equation of the asymptote of the curve.\\
(ii) Show that $- \frac { 1 } { 6 } \leqslant y \leqslant \frac { 1 } { 2 }$.

\hfill \mbox{\textit{OCR FP2 2006 Q3 [6]}}