AQA FP1 2015 June — Question 8 11 marks

Exam BoardAQA
ModuleFP1 (Further Pure Mathematics 1)
Year2015
SessionJune
Marks11
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicCurve Sketching
TypeRange restriction with discriminant (quadratic denominator)
DifficultyChallenging +1.2 This is a multi-part FP1 question requiring algebraic manipulation to find range restrictions and stationary points. Part (a) is routine (identifying y=0 asymptote). Part (b) requires rearranging to form a quadratic in x and applying the discriminant condition, which is a standard technique. Part (c) cleverly uses the discriminant result to find stationary points without calculus—this requires insight but is a well-known FP1 method. Overall, slightly above average difficulty due to the non-routine approach in part (c), but still a standard exam question testing core techniques.
Spec1.02d Quadratic functions: graphs and discriminant conditions1.02g Inequalities: linear and quadratic in single variable1.02k Simplify rational expressions: factorising, cancelling, algebraic division

8 A curve \(C\) has equation $$y = \frac { x ( x - 3 ) } { x ^ { 2 } + 3 }$$
  1. State the equation of the asymptote of \(C\).
  2. The line \(y = k\) intersects the curve \(C\). Show that \(4 k ^ { 2 } - 4 k - 3 \leqslant 0\).
  3. Hence find the coordinates of the stationary points of the curve \(C\). (No credit will be given for solutions based on differentiation.) \includegraphics[max width=\textwidth, alt={}, center]{e45b07a3-e303-4caf-8f3a-5341bad7560a-24_2488_1728_219_141}

Question 1
(a) [2 marks]
- M1: Apply Vieta's formulas to \(2x^2 + 6x + 7 = 0\)
- A1: \(a + b = -3\) and \(ab = 3.5\) (or \(\frac{7}{2}\))
(b) [5 marks]
- M1: Find \(a^2 - 1 + b^2 - 1 = (a+b)^2 - 2ab - 2\)
- M1: Calculate \((a+b)^2 - 2ab - 2 = 9 - 7 - 2 = 0\)
- M1: Find \((a^2-1)(b^2-1) = a^2b^2 - a^2 - b^2 + 1\)
- M1: Calculate \(a^2b^2 - (a^2 + b^2) + 1 = 12.25 - 7 + 1 = 6.25\)
- A1: Quadratic equation is \(4x^2 - 25 = 0\) (or equivalent with integer coefficients)
(c) [2 marks]
- M1: Use roots of quadratic from part (b)
- A1: \(a^2 = \frac{5}{2}\) and \(b^2 = \frac{5}{2}\) (or \(a^2 = 2.5\), \(b^2 = 2.5\))
Question 2
(a) [1 mark]
- B1: The integrand has a singularity (vertical asymptote) at \(x = 0\) within the interval of integration
(b) [4 marks]
- M1: Set up limit: \(\lim_{\epsilon \to 0^+} \int_{\epsilon}^{4} (4x - 4)x^{-1.5} \, dx\)
- M1: Integrate to get \(\left[-8x^{0.5} - 8x^{-0.5}\right]_{\epsilon}^{4}\)
- M1: Evaluate at limits
- DM1: Take limit as \(\epsilon \to 0^+\)
- A1: The integral does not have a finite value (or explain divergence to \(-\infty\))
Question 3
(a) [3 marks]
- M1: Rationalize \(\frac{3}{2+i}\) by multiplying by \(\frac{2-i}{2-i}\)
- M1: Calculate numerator and denominator
- A1: \((2+i)^3 = 2 + 11i\) (expressed in form \(2 + bi\) where \(b = 11\))
(b)(i) [4 marks]
- M1: Substitute \(z = 2 + i\) into \(z^3 + pz + q = 0\)
- M1: Calculate \((2+i)^3 = 2 + 11i\)
- M1: Set up equation \((2 + 11i) + p(2+i) + q = 0\)
- M1: Equate real and imaginary parts
- A1: \(p = -11\) and \(q = -50\)
(b)(ii) [2 marks]
- M1: Use that \(2-i\) is also a root (complex conjugate pair)
- A1: Quadratic factor is \(z^2 - 4z + 5\) (or equivalent)
(b)(iii) [2 marks]
- M1: Divide \(z^3 - 11z - 50\) by \(z^2 - 4z + 5\)
- A1: Real root is \(z = -2\)
Question 4
(a) [5 marks]
- M1: Solve \(\sin(3x + 45°) = \frac{1}{2}\)
- M1: Identify general angles: \(3x + 45° = 30° + 360°n\) or \(3x + 45° = 150° + 360°n\)
- M1: Rearrange to find \(x\)
- A1: \(x = -5° + 120°n\) or \(x = 35° + 120°n\)
- A1: Complete general solution stated clearly
(b) [1 mark]
- A1: Solution closest to \(200°\) is \(x = 155°\) (or appropriate value from general solution)
Question 5
(a) [4 marks]
- M1: Set up matrix equation \(\begin{pmatrix} -2 & c \\ d & 3 \end{pmatrix} \begin{pmatrix} 5 \\ 2 \end{pmatrix} = \begin{pmatrix} -2 \\ 1 \end{pmatrix}\)
- M1: Form equations \(-10 + 2c = -2\) and \(5d + 6 = 1\)
- A1: \(c = 4\)
- A1: \(d = -1\)
(b)(i) [2 marks]
- M1: Calculate successive powers of \(B\)
- A1: \(B^4 = 4I\) (so \(k = 4\))
(b)(ii) [5 marks]
- B1: Identify that \(B\) represents a rotation (by \(45°\) counterclockwise)
- B1: Identify that \(B\) represents a scaling (by factor \(\sqrt{2}\))
- A1: Described as rotation by \(45°\) combined with enlargement scale factor \(\sqrt{2}\)
- A1: Clear description of order and combination
- A1: Centre of rotation stated (origin) if required
(b)(iii) [2 marks]
- M1: Use \(B^{17} = B^{16} \cdot B = (B^4)^4 \cdot B = (4I)^4 \cdot B = 256I \cdot B\)
- A1: \(B^{17} = 256B = \begin{pmatrix} 128\sqrt{2} & 128\sqrt{2} \\ -128\sqrt{2} & 128\sqrt{2} \end{pmatrix}\) (or equivalent form)
Question 6
(a) [2 marks]
- B1: Sketch of hyperbola with correct shape and orientation
- A1: State intercepts: \((\pm 3, 0)\); no \(y\)-intercepts
(b) [3 marks]
- M1: Apply translation to get equation of \(C_2\)
- M1: Use condition that \(C_2\) passes through origin
- A1: Asymptotes are \(y = \pm \frac{4}{3}(x + 3)\) (or equivalent form)
Question 7
(a)(i) [2 marks]
- M1: Evaluate \(f(39)\) and \(f(40)\) for \(f(x) = 2x^3 + 5x^2 + 3x - 132000\)
- A1: Show sign change confirms \(39 < a < 40\)
(a)(ii) [3 marks]
- M1: Apply Newton-Raphson: \(x_2 = x_1 - \frac{f(x_1)}{f'(x_1)}\) with \(x_1 = 40\)
- M1: Calculate \(f(40)\) and \(f'(40) = 6x^2 + 10x + 3\)
- A1: \(x_2 = 39.49\) (to 2 d.p.)
(b) [5 marks]
- M1: Expand \(2r(3r + 2) = 6r^2 + 4r\)
- M1: Write as $\Sigma 6r^2 + 4\Sigma
# Question 1

**(a)** [2 marks]
- M1: Apply Vieta's formulas to $2x^2 + 6x + 7 = 0$
- A1: $a + b = -3$ and $ab = 3.5$ (or $\frac{7}{2}$)

**(b)** [5 marks]
- M1: Find $a^2 - 1 + b^2 - 1 = (a+b)^2 - 2ab - 2$
- M1: Calculate $(a+b)^2 - 2ab - 2 = 9 - 7 - 2 = 0$
- M1: Find $(a^2-1)(b^2-1) = a^2b^2 - a^2 - b^2 + 1$
- M1: Calculate $a^2b^2 - (a^2 + b^2) + 1 = 12.25 - 7 + 1 = 6.25$
- A1: Quadratic equation is $4x^2 - 25 = 0$ (or equivalent with integer coefficients)

**(c)** [2 marks]
- M1: Use roots of quadratic from part (b)
- A1: $a^2 = \frac{5}{2}$ and $b^2 = \frac{5}{2}$ (or $a^2 = 2.5$, $b^2 = 2.5$)

---

# Question 2

**(a)** [1 mark]
- B1: The integrand has a singularity (vertical asymptote) at $x = 0$ within the interval of integration

**(b)** [4 marks]
- M1: Set up limit: $\lim_{\epsilon \to 0^+} \int_{\epsilon}^{4} (4x - 4)x^{-1.5} \, dx$
- M1: Integrate to get $\left[-8x^{0.5} - 8x^{-0.5}\right]_{\epsilon}^{4}$
- M1: Evaluate at limits
- DM1: Take limit as $\epsilon \to 0^+$
- A1: The integral does not have a finite value (or explain divergence to $-\infty$)

---

# Question 3

**(a)** [3 marks]
- M1: Rationalize $\frac{3}{2+i}$ by multiplying by $\frac{2-i}{2-i}$
- M1: Calculate numerator and denominator
- A1: $(2+i)^3 = 2 + 11i$ (expressed in form $2 + bi$ where $b = 11$)

**(b)(i)** [4 marks]
- M1: Substitute $z = 2 + i$ into $z^3 + pz + q = 0$
- M1: Calculate $(2+i)^3 = 2 + 11i$
- M1: Set up equation $(2 + 11i) + p(2+i) + q = 0$
- M1: Equate real and imaginary parts
- A1: $p = -11$ and $q = -50$

**(b)(ii)** [2 marks]
- M1: Use that $2-i$ is also a root (complex conjugate pair)
- A1: Quadratic factor is $z^2 - 4z + 5$ (or equivalent)

**(b)(iii)** [2 marks]
- M1: Divide $z^3 - 11z - 50$ by $z^2 - 4z + 5$
- A1: Real root is $z = -2$

---

# Question 4

**(a)** [5 marks]
- M1: Solve $\sin(3x + 45°) = \frac{1}{2}$
- M1: Identify general angles: $3x + 45° = 30° + 360°n$ or $3x + 45° = 150° + 360°n$
- M1: Rearrange to find $x$
- A1: $x = -5° + 120°n$ or $x = 35° + 120°n$
- A1: Complete general solution stated clearly

**(b)** [1 mark]
- A1: Solution closest to $200°$ is $x = 155°$ (or appropriate value from general solution)

---

# Question 5

**(a)** [4 marks]
- M1: Set up matrix equation $\begin{pmatrix} -2 & c \\ d & 3 \end{pmatrix} \begin{pmatrix} 5 \\ 2 \end{pmatrix} = \begin{pmatrix} -2 \\ 1 \end{pmatrix}$
- M1: Form equations $-10 + 2c = -2$ and $5d + 6 = 1$
- A1: $c = 4$
- A1: $d = -1$

**(b)(i)** [2 marks]
- M1: Calculate successive powers of $B$
- A1: $B^4 = 4I$ (so $k = 4$)

**(b)(ii)** [5 marks]
- B1: Identify that $B$ represents a rotation (by $45°$ counterclockwise)
- B1: Identify that $B$ represents a scaling (by factor $\sqrt{2}$)
- A1: Described as rotation by $45°$ combined with enlargement scale factor $\sqrt{2}$
- A1: Clear description of order and combination
- A1: Centre of rotation stated (origin) if required

**(b)(iii)** [2 marks]
- M1: Use $B^{17} = B^{16} \cdot B = (B^4)^4 \cdot B = (4I)^4 \cdot B = 256I \cdot B$
- A1: $B^{17} = 256B = \begin{pmatrix} 128\sqrt{2} & 128\sqrt{2} \\ -128\sqrt{2} & 128\sqrt{2} \end{pmatrix}$ (or equivalent form)

---

# Question 6

**(a)** [2 marks]
- B1: Sketch of hyperbola with correct shape and orientation
- A1: State intercepts: $(\pm 3, 0)$; no $y$-intercepts

**(b)** [3 marks]
- M1: Apply translation to get equation of $C_2$
- M1: Use condition that $C_2$ passes through origin
- A1: Asymptotes are $y = \pm \frac{4}{3}(x + 3)$ (or equivalent form)

---

# Question 7

**(a)(i)** [2 marks]
- M1: Evaluate $f(39)$ and $f(40)$ for $f(x) = 2x^3 + 5x^2 + 3x - 132000$
- A1: Show sign change confirms $39 < a < 40$

**(a)(ii)** [3 marks]
- M1: Apply Newton-Raphson: $x_2 = x_1 - \frac{f(x_1)}{f'(x_1)}$ with $x_1 = 40$
- M1: Calculate $f(40)$ and $f'(40) = 6x^2 + 10x + 3$
- A1: $x_2 = 39.49$ (to 2 d.p.)

**(b)** [5 marks]
- M1: Expand $2r(3r + 2) = 6r^2 + 4r$
- M1: Write as $\Sigma 6r^2 + 4\Sigma
8 A curve $C$ has equation

$$y = \frac { x ( x - 3 ) } { x ^ { 2 } + 3 }$$
\begin{enumerate}[label=(\alph*)]
\item State the equation of the asymptote of $C$.
\item The line $y = k$ intersects the curve $C$. Show that $4 k ^ { 2 } - 4 k - 3 \leqslant 0$.
\item Hence find the coordinates of the stationary points of the curve $C$. (No credit will be given for solutions based on differentiation.)\\
\includegraphics[max width=\textwidth, alt={}, center]{e45b07a3-e303-4caf-8f3a-5341bad7560a-24_2488_1728_219_141}
\end{enumerate}

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