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Thinka Jun 2024 (V2) Cambridge International A Level-Style Mock — Further Pure Mathematics

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An original Thinka practice paper modelled on the structure and difficulty of the Jun 2024 (V2) Cambridge International A Level Further Pure Mathematics paper. Not affiliated with or reproduced from Cambridge.

Paper 1R

Answer all questions. Calculators may be used. Show all stages in your working.
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PastPaper.question 1 · Short Answer
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The curve \( C \) has equation \( y = \frac{3x - 1}{x^2 + 2} \). Find an equation of the normal to \( C \) at the point where \( C \) crosses the \( y \)-axis. Give your answer in the form \( ax + by + c = 0 \), where \( a \), \( b \), and \( c \) are integers.
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First, find the coordinates of the point where the curve \( C \) crosses the \( y \)-axis by setting \( x = 0 \). This gives \( y = \frac{3(0) - 1}{0^2 + 2} = -\frac{1}{2} \). So the point of contact is \( (0, -0.5) \). Next, find the gradient of the curve by differentiating \( y \) with respect to \( x \) using the quotient rule: \( \frac{dy}{dx} = \frac{3(x^2 + 2) - (3x - 1)(2x)}{(x^2 + 2)^2} \). Evaluating this derivative at \( x = 0 \) gives \( \frac{dy}{dx} = \frac{3(2) - 0}{2^2} = \frac{6}{4} = \frac{3}{2} \). The gradient of the normal is the negative reciprocal of the gradient of the tangent, which is \( m_n = -\frac{2}{3} \). Using the equation of a straight line, the equation of the normal is \( y - y_1 = m_n(x - x_1) \), which gives \( y - \left(-\frac{1}{2}\right) = -\frac{2}{3}(x - 0) \). Simplifying this equation gives \( y + \frac{1}{2} = -\frac{2}{3}x \), which can be rewritten as \( 6y + 3 = -4x \), or \( 4x + 6y + 3 = 0 \).

PastPaper.markingScheme

M1: For substituting \( x = 0 \) into the equation of the curve to find the \( y \)-coordinate. A1: Correctly obtaining \( y = -0.5 \) (or equivalent). M1: For applying the quotient rule correctly to differentiate \( y = \frac{3x - 1}{x^2 + 2} \). A1: Correctly finding the gradient of the tangent at \( x = 0 \) is \( \frac{3}{2} \). M1: For finding the gradient of the normal as the negative reciprocal of their tangent gradient. A0.5: Formulating the equation of the normal and simplifying to the required form \( 4x + 6y + 3 = 0 \) (or any non-zero integer multiple thereof).
PastPaper.question 2 · Short Answer
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Solve, for \( 0 \le \theta < 360^\circ \), the equation \( 3\cos 2\theta + 5\sin \theta - 4 = 0 \). Give your answers to 1 decimal place where appropriate.
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PastPaper.workedSolution

Use the double-angle identity \( \cos 2\theta = 1 - 2\sin^2\theta \) to rewrite the equation in terms of \( \sin\theta \) only: \( 3(1 - 2\sin^2\theta) + 5\sin\theta - 4 = 0 \). Expanding and simplifying gives \( 3 - 6\sin^2\theta + 5\sin\theta - 4 = 0 \), which simplifies to \( 6\sin^2\theta - 5\sin\theta + 1 = 0 \). This quadratic equation can be factorised as \( (2\sin\theta - 1)(3\sin\theta - 1) = 0 \). This gives two possible values: \( \sin\theta = \frac{1}{2} \) or \( \sin\theta = \frac{1}{3} \). For \( \sin\theta = \frac{1}{2} \) within the range \( 0 \le \theta < 360^\circ \), the solutions are \( \theta = 30^\circ \) and \( \theta = 180^\circ - 30^\circ = 150^\circ \). For \( \sin\theta = \frac{1}{3} \), the principal value is \( \theta = \sin^{-1}\left(\frac{1}{3}\right) \approx 19.5^\circ \), and the second value is \( \theta = 180^\circ - 19.5^\circ = 160.5^\circ \). Thus, the full set of solutions is \( \theta = 19.5^\circ, 30^\circ, 150^\circ, 160.5^\circ \).

PastPaper.markingScheme

M1: Substituting \( \cos 2\theta = 1 - 2\sin^2\theta \) into the equation. A0.5: Formulating a correct quadratic equation in terms of \( \sin\theta \): \( 6\sin^2\theta - 5\sin\theta + 1 = 0 \). M1: Solving the quadratic equation to obtain two values for \( \sin\theta \). A1.5: Obtaining \( \sin\theta = \frac{1}{2} \) and \( \sin\theta = \frac{1}{3} \). A0.75: Identifying the angles \( 30^\circ \) and \( 150^\circ \) from \( \sin\theta = \frac{1}{2} \). A0.75: Identifying the angles \( 19.5^\circ \) and \( 160.5^\circ \) from \( \sin\theta = \frac{1}{3} \), rounded to 1 decimal place.
PastPaper.question 3 · Short Answer
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The sum of the first \( n \) terms of an arithmetic series is given by \( S_n = 2n^2 + 5n \). Given that the \( k \)-th term of this series is 103, find the value of \( k \).
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PastPaper.workedSolution

The sum of the first \( n \) terms is \( S_n = 2n^2 + 5n \). We can find the first term \( a \) by evaluating \( S_1 \): \( a = S_1 = 2(1)^2 + 5(1) = 7 \). The sum of the first two terms is \( S_2 = 2(2)^2 + 5(2) = 8 + 10 = 18 \). Since \( S_2 = u_1 + u_2 = a + u_2 \), the second term is \( u_2 = S_2 - S_1 = 18 - 7 = 11 \). The common difference \( d \) of the arithmetic series is \( d = u_2 - a = 11 - 7 = 4 \). The general expression for the \( k \)-th term of an arithmetic series is \( u_k = a + (k - 1)d \). Substituting our values, we get \( u_k = 7 + (k - 1)4 = 4k + 3 \). Since the \( k \)-th term is 103, we can set up the equation \( 4k + 3 = 103 \). Solving for \( k \) gives \( 4k = 100 \), which simplifies to \( k = 25 \).

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M1: Attempting to find \( S_1 \) and \( S_2 \) or using an alternative valid method to find terms of the series. A0.5: Correctly finding \( a = 7 \). M1: Finding the second term \( u_2 = 11 \) or establishing the common difference \( d = 4 \). A1: Correctly writing the general term of the series as \( u_k = 4k + 3 \). M1: Setting up the linear equation \( 4k + 3 = 103 \) to solve for \( k \). A1: Obtaining \( k = 25 \).
PastPaper.question 4 · Short Answer
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Solve the simultaneous equations: \( \log_2(x - 2y) = 3 \) and \( 3^x \cdot 9^y = 27^5 \).
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PastPaper.workedSolution

From the first equation, \( \log_2(x - 2y) = 3 \), we can rewrite this in exponential form: \( x - 2y = 2^3 \), which simplifies to \( x - 2y = 8 \) (Equation 1). From the second equation, \( 3^x \cdot 9^y = 27^5 \), we can express all terms with base 3: \( 3^x \cdot (3^2)^y = (3^3)^5 \), which simplifies to \( 3^{x + 2y} = 3^{15} \). Equating the indices gives \( x + 2y = 15 \) (Equation 2). We now have a system of two linear equations: 1) \( x - 2y = 8 \) and 2) \( x + 2y = 15 \). Adding the two equations together: \( (x - 2y) + (x + 2y) = 8 + 15 \implies 2x = 23 \implies x = 11.5 \). Substituting \( x = 11.5 \) back into Equation 2: \( 11.5 + 2y = 15 \implies 2y = 3.5 \implies y = 1.75 \). Checking both values in \( x - 2y > 0 \) confirms that they are valid solutions.

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M1: Converting the logarithmic equation into the linear equation \( x - 2y = 8 \). A0.5: Correctly simplified linear equation from log. M1: Expressing the second equation using a common base of 3 and equating powers. A1: Correctly obtaining the linear equation \( x + 2y = 15 \). M1: Attempting to solve the system of two simultaneous linear equations. A1: Correctly finding both \( x = 11.5 \) and \( y = 1.75 \) (or equivalent fractional values \( x = \frac{23}{2} \) and \( y = \frac{7}{4} \)).
PastPaper.question 5 · Structured
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A closed right circular cylinder has radius \(r\) cm and height \(h\) cm. The total surface area of the cylinder is \(150\pi\) cm\(^2\). (a) Show that the volume, \(V\) cm\(^3\), of the cylinder is given by \(V = 75\pi r - \pi r^3\). (4 marks) (b) Use calculus to find the maximum volume of the cylinder, leaving your answer in terms of \(\pi\). (5 marks) (c) Justify that your value is indeed a maximum. (2 marks)
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PastPaper.workedSolution

(a) The total surface area of a closed cylinder is given by \(A = 2\pi r^2 + 2\pi r h = 150\pi\). This simplifies to \(2\pi r h = 150\pi - 2\pi r^2\), which gives \(h = \frac{150\pi - 2\pi r^2}{2\pi r} = \frac{75 - r^2}{r}\). The volume of the cylinder is \(V = \pi r^2 h = \pi r^2 \left(\frac{75 - r^2}{r}\right) = \pi r (75 - r^2) = 75\pi r - \pi r^3\). (b) Differentiating \(V\) with respect to \(r\) gives \(\frac{dV}{dr} = 75\pi - 3\pi r^2\). Setting \(\frac{dV}{dr} = 0\) for stationary points gives \(75\pi - 3\pi r^2 = 0 \implies 3r^2 = 75 \implies r^2 = 25\). Since \(r > 0\), we have \(r = 5\). Substituting \(r = 5\) back into the volume formula gives \(V = 75\pi(5) - \pi(5)^3 = 375\pi - 125\pi = 250\pi\) cm\(^3\). (c) The second derivative is \(\frac{d^2V}{dr^2} = -6\pi r\). At \(r = 5\), \(\frac{d^2V}{dr^2} = -30\pi < 0\). Since the second derivative is negative, the volume is a maximum.

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(a) M1: Attempts to write an equation for the total surface area and sets equal to \(150\pi\). M1: Rearranges to express \(h\) in terms of \(r\). M1: Substitutes expression for \(h\) into the volume formula \(V = \pi r^2 h\). A1: Correctly simplifies to show \(V = 75\pi r - \pi r^3\) (no errors seen). (b) M1: Correctly differentiates \(V\) to find \(\frac{dV}{dr}\). M1: Sets derivative equal to zero. A1: Solves to find \(r = 5\) (accepts \(r = \pm 5\) but must reject negative for final A1). M1: Substitutes \(r = 5\) into the volume equation. A1: Correct volume of \(250\pi\). (c) M1: Differentiates again to find the second derivative \(\frac{d^2V}{dr^2}\). A1: Evaluates at \(r = 5\) and states that since it is less than 0, it is a maximum.
PastPaper.question 6 · Structured
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(a) Show that the equation \(3 \cos 2\theta + 8 \sin \theta + 5 = 0\) can be written in the form \(6 \sin^2 \theta - 8 \sin \theta - 8 = 0\). (3 marks) (b) Solve, to the nearest degree, the equation \(3 \cos 2\theta + 8 \sin \theta + 5 = 0\) for \(0^\circ \le \theta \le 360^\circ\). (5 marks) (c) Hence, solve \(3 \cos (4x - 20^\circ) + 8 \sin (2x - 10^\circ) + 5 = 0\) for \(0^\circ \le x \le 180^\circ\). (3 marks)
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PastPaper.workedSolution

(a) Using the identity \ \cos 2\theta = 1 - 2\sin^2\theta\, we substitute this into the equation: \(3(1 - 2\sin^2\theta) + 8\sin\theta + 5 = 0\). Expanding and simplifying gives: \(3 - 6\sin^2\theta + 8\sin\theta + 5 = 0 \implies -6\sin^2\theta + 8\sin\theta + 8 = 0\). Multiplying the entire equation by \(-1\) gives the required form: \(6\sin^2\theta - 8\sin\theta - 8 = 0\). (b) We let \(y = \sin\theta\), so the equation is \(6y^2 - 8y - 8 = 0\). Dividing by 2: \(3y^2 - 4y - 4 = 0\). Factoring gives \((3y + 2)(y - 2) = 0\). Thus, \\sin\theta = -\frac{2}{3}\ or \(\sin\theta = 2\) (which has no real solutions). For \(\sin\theta = -\frac{2}{3}\), the basic acute angle is \(\sin^{-1}(2/3) \approx 41.81^\circ\). Since sine is negative, \(\theta\) lies in the third and fourth quadrants: \(\theta = 180^\circ + 41.81^\circ = 221.81^\circ \approx 222^\circ\) and \(\theta = 360^\circ - 41.81^\circ = 318.19^\circ \approx 318^\circ\). (c) Comparing the equations, let \(\theta = 2x - 10^\circ\). The range \(0^\circ \le x \le 180^\circ\) becomes \(-10^\circ \le 2x - 10^\circ \le 350^\circ\). In this range, our solutions for \(\theta\) are \(221.81^\circ\) and \(318.19^\circ\). For \(2x - 10^\circ = 221.81^\circ \implies 2x = 231.81^\circ \implies x \approx 115.9^\circ\). For \(2x - 10^\circ = 318.19^\circ \implies 2x = 328.19^\circ \implies x \approx 164.1^\circ\). To the nearest degree, \(x = 116^\circ\) or \(x = 164^\circ\).

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(a) M1: Uses the double angle identity \(\cos 2\theta = 1 - 2\sin^2\theta\). M1: Substitutes and simplifies terms. A1: Correctly reaches the given equation. (b) M1: Solves the quadratic in \(\sin\theta\) (by factoring, formula or calculator). A1: Identifies \(\sin\theta = -2/3\) and states no solution for \(\sin\theta = 2\). M1: Finds one correct value for \(\theta\) in the range. A1: Finds \(222^\circ\) (accept 221.8). A1: Finds \(318^\circ\) (accept 318.2). (c) M1: Connects the two equations by setting \(\theta = 2x - 10^\circ\). A1: Correctly solves for one value of \(x\) (116 or 164). A1: Finds both correct values of \(x\) (116 and 164) to the nearest degree.
PastPaper.question 7 · Structured
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The first three terms of a geometric series \(G\) are \(k+4\), \(k\), and \(2k-15\) respectively, where \(k\) is a positive constant. (a) Show that \(k^2 - 7k - 60 = 0\). (3 marks) (b) Find the value of \(k\). (2 marks) (c) Find the sum to infinity of \(G\). (3 marks) (d) An arithmetic series \(A\) has first term \(a\) and common difference \(d\). The 3rd term of \(A\) is equal to the 3rd term of \(G\). The 10th term of \(A\) is equal to 37. Find the sum of the first 20 terms of \(A\). (3 marks)
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PastPaper.workedSolution

(a) Since the terms are in geometric progression, the common ratio is constant: \(\frac{k}{k+4} = \frac{2k-15}{k}\). Cross-multiplying gives \(k^2 = (k+4)(2k-15) \implies k^2 = 2k^2 - 15k + 8k - 60 \implies k^2 = 2k^2 - 7k - 60\). Rearranging gives the required quadratic: \(k^2 - 7k - 60 = 0\). (b) Factoring the quadratic: \((k-12)(k+5) = 0\). Since \(k > 0\), we must have \(k = 12\). (c) For \(k = 12\), the first three terms of \(G\) are: \(a_G = 16\), \(12\), and \(9\). The common ratio is \(r = \frac{12}{16} = 0.75\). The sum to infinity is \(S_\infty = \frac{a_G}{1-r} = \frac{16}{1 - 0.75} = \frac{16}{0.25} = 64\). (d) The 3rd term of \(G\) is 9, so the 3rd term of \(A\) is \(a + 2d = 9\). The 10th term of \(A\) is \(a + 9d = 37\). Subtracting these two equations: \(7d = 28 \implies d = 4\). Substituting back gives \(a + 2(4) = 9 \implies a = 1\). The sum of the first 20 terms is \(S_{20} = \frac{20}{2}[2a + 19d] = 10[2(1) + 19(4)] = 10[2 + 76] = 780\).

PastPaper.markingScheme

(a) M1: Uses the common ratio property of a GP to set up a fractional equation. M1: Expands parentheses and simplifies. A1: Obtains the correct quadratic equation without any errors. (b) M1: Solves the quadratic equation. A1: Chooses \(k = 12\) and rejects \(k = -5\). (c) M1: Evaluates the first term and common ratio of \(G\). M1: Uses the sum to infinity formula with their values of \(a\) and \(r\). A1: Correctly obtains 64. (d) M1: Sets up two simultaneous equations for \(a\) and \(d\). A1: Solves to find \(a = 1\) and \(d = 4\). A1: Applies sum formula of AP to obtain 780.
PastPaper.question 8 · Structured
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Relative to a fixed origin \(O\), the position vector of the point \(A\) is \(-\mathbf{i} - \mathbf{j}\) and the position vector of the point \(B\) is \(7\mathbf{i} - 7\mathbf{j}\). (a) Find the vector \(\overrightarrow{AB}\) and calculate its magnitude \(|\overrightarrow{AB}|\). (3 marks) (b) The point \(C\) is the midpoint of \(AB\). Find the position vector of \(C\). (3 marks) (c) The point \(D\) has position vector \(\lambda\mathbf{i} + 6\mathbf{j}\), where \(\lambda\) is a constant. Given that the vector \(\overrightarrow{OD}\) is perpendicular to \(\overrightarrow{OC}\), find the value of \(\lambda\). (3 marks) (d) Find the unit vector in the direction of \(\overrightarrow{OC}\). (2 marks)
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PastPaper.workedSolution

(a) The vector \(\overrightarrow{AB} = \mathbf{b} - \mathbf{a} = (7\mathbf{i} - 7\mathbf{j}) - (-\mathbf{i} - \mathbf{j}) = 8\mathbf{i} - 6\mathbf{j}\). The magnitude is \(|\overrightarrow{AB}| = \sqrt{8^2 + (-6)^2} = \sqrt{64 + 36} = 10\). (b) Since \(C\) is the midpoint of \(AB\), \(\overrightarrow{OC} = \frac{1}{2}(\mathbf{a} + \mathbf{b}) = \frac{1}{2}((-\mathbf{i} - \mathbf{j}) + (7\mathbf{i} - 7\mathbf{j})) = \frac{1}{2}(6\mathbf{i} - 8\mathbf{j}) = 3\mathbf{i} - 4\mathbf{j}\). (c) Given \(\overrightarrow{OD} = \lambda\mathbf{i} + 6\mathbf{j}\) is perpendicular to \(\overrightarrow{OC}\), their scalar product must be zero: \(\overrightarrow{OD} \cdot \overrightarrow{OC} = 0 \implies (\lambda\mathbf{i} + 6\mathbf{j}) \cdot (3\mathbf{i} - 4\mathbf{j}) = 0 \implies 3\lambda - 24 = 0 \implies 3\lambda = 24 \implies \lambda = 8\). (d) The magnitude of \(\overrightarrow{OC}\) is \(|\overrightarrow{OC}| = \sqrt{3^2 + (-4)^2} = 5\). The unit vector is \(\frac{\overrightarrow{OC}}{|\overrightarrow{OC}|} = \frac{3\mathbf{i} - 4\mathbf{j}}{5} = 0.6\mathbf{i} - 0.8\mathbf{j}\).

PastPaper.markingScheme

(a) M1: Calculates \(\mathbf{b} - \mathbf{a}\) to find \(\overrightarrow{AB}\). A1: Correct vector \(8\mathbf{i} - 6\mathbf{j}\). A1: Correct magnitude of 10. (b) M1: Employs midpoint formula \(\frac{\mathbf{a}+\mathbf{b}}{2}\). A1: Correct \(\mathbf{i}\) component (3). A1: Correct \(\mathbf{j}\) component (-4). (c) M1: Set up the dot product equation \(\overrightarrow{OD} \cdot \overrightarrow{OC} = 0\). A1: Correctly expands to obtain \(3\lambda - 24 = 0\). A1: Solves to find \(\lambda = 8\). (d) M1: Attempts to divide \(\overrightarrow{OC}\) by its magnitude (5). A1: Correct unit vector \(0.6\mathbf{i} - 0.8\mathbf{j}\) (or in fraction form).
PastPaper.question 9 · Structured
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A curve \(C\) has equation \(y = (x-2)(x-4)^2\). (a) Find the coordinates of the stationary points of \(C\). (5 marks) (b) Sketch the curve \(C\), showing the coordinates of the points where the curve meets or crosses the coordinate axes. (3 marks) (c) Find the area of the finite region bounded by the curve \(C\) and the x-axis. (3 marks)
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PastPaper.workedSolution

(a) Expand the equation of the curve: \(y = (x-2)(x^2 - 8x + 16) = x^3 - 8x^2 + 16x - 2x^2 + 16x - 32 = x^3 - 10x^2 + 32x - 32\). Differentiating with respect to \(x\): \(\frac{dy}{dx} = 3x^2 - 20x + 32\). Set the derivative to zero for stationary points: \(3x^2 - 20x + 32 = 0 \implies (3x - 8)(x - 4) = 0\). So \(x = 4\) or \(x = \frac{8}{3}\). When \(x = 4\), \(y = (4-2)(4-4)^2 = 0\). Stationary point is \((4, 0)\). When \(x = \frac{8}{3}\), \(y = (\frac{8}{3} - 2)(\frac{8}{3} - 4)^2 = (\frac{2}{3})(-\frac{4}{3})^2 = \frac{32}{27}\). Stationary point is \((\frac{8}{3}, \frac{32}{27})\). (b) When \(x = 0\), \(y = (0-2)(0-4)^2 = -32\). Thus the y-intercept is \((0, -32)\). When \(y = 0\), \(x = 2\) or \(x = 4\). The curve touches the x-axis at \((4,0)\) and crosses it at \((2,0)\). The sketch should show a cubic curve starting in quadrant 3, crossing the y-axis at \((0,-32)\), crossing the x-axis at \((2,0)\), reaching a maximum at \((\frac{8}{3}, \frac{32}{27})\), turning at a minimum at \((4,0)\), and increasing for \(x > 4\). (c) The region is bounded between \(x = 2\) and \(x = 4\). The area is: \(\int_{2}^{4} (x^3 - 10x^2 + 32x - 32) \, dx = \left[ \frac{1}{4}x^4 - \frac{10}{3}x^3 + 16x^2 - 32x \right]_{2}^{4}\). At \(x = 4\): \(\frac{256}{4} - \frac{640}{3} + 256 - 128 = 192 - \frac{640}{3} = -\frac{64}{3}\). At \(x = 2\): \(\frac{16}{4} - \frac{80}{3} + 64 - 64 = 4 - \frac{80}{3} = -\frac{68}{3}\). Area = \(-\frac{64}{3} - (-\frac{68}{3}) = \frac{4}{3}\).

PastPaper.markingScheme

(a) M1: Expands the expression of \(y\) correctly. M1: Differentiates to find \(\frac{dy}{dx}\). M1: Sets derivative to 0 and solves quadratic. A1: Obtains \((4, 0)\). A1: Obtains \((8/3, 32/27)\). (b) M1: Finds intercept on y-axis \((0, -32)\) and intercepts on x-axis \((2,0)\), \((4,0)\). A1: Correct shape of positive cubic curve. A1: Completely labelled sketch with all key coordinates shown. (c) M1: Integrates the expanded polynomial expression. A1: Substitutes limits 2 and 4 correctly. A1: Correctly evaluates the area to obtain \(4/3\).
PastPaper.question 10 · Structured
11 PastPaper.marks
A curve has equation \(y = \frac{3x - 5}{2x + 4}\). (a) State the equations of the asymptotes of the curve. (2 marks) (b) Find the coordinates of the points where the curve intersects the coordinate axes. (2 marks) (c) Sketch the curve, showing clearly the asymptotes and the coordinates of the points of intersection with the axes. (4 marks) (d) Find the coordinates of the points of intersection of the curve with the straight line \(y = x - 3\). (3 marks)
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PastPaper.workedSolution

(a) The vertical asymptote occurs where the denominator is zero: \(2x + 4 = 0 \implies x = -2\). The horizontal asymptote is found by taking the limit as \(x \to \pm\infty\): \(y = \frac{3}{2}\). (b) Intersection with y-axis (set \(x=0\)): \(y = \frac{-5}{4} = -1.25\). Point is \((0, -1.25)\). Intersection with x-axis (set \(y=0\)): \(3x - 5 = 0 \implies x = \frac{5}{3}\). Point is \((\frac{5}{3}, 0)\). (c) The sketch should show a rectangular hyperbola with branches in the top-right and bottom-left regions formed by the asymptotes \(x = -2\) and \(y = 1.5\). It must clearly show the intersections with the axes at \((0, -1.25)\) and \((\frac{5}{3}, 0)\). (d) To find the intersections, set the equations equal: \\frac{3x - 5}{2x + 4} = x - 3 \implies 3x - 5 = (x - 3)(2x + 4) = 2x^2 - 2x - 12\). Rearranging gives: \(2x^2 - 5x - 7 = 0 \implies (2x - 7)(x + 1) = 0\). The x-coordinates are \(x = -1\) and \(x = 3.5\). Substituting into \(y = x - 3\): for \(x = -1\), \(y = -4\); for \(x = 3.5\), \(y = 0.5\). The points are \((-1, -4)\) and \((3.5, 0.5)\).

PastPaper.markingScheme

(a) A1: Correct vertical asymptote \(x = -2\). A1: Correct horizontal asymptote \(y = 1.5\) (or \(y = 3/2\)). (b) A1: Correct y-intercept \((0, -1.25)\). A1: Correct x-intercept \((5/3, 0)\). (c) M1: Draws a hyperbola with two branches. A1: Correct asymptotes drawn and labelled. A1: Intersects the axes in correct quadrants. A1: All four key features (2 asymptotes, 2 intercepts) correctly labelled with coordinates. (d) M1: Equates the curve and line, clears denominator to get a quadratic. A1: Solves to get \(x = -1\) and \(x = 3.5\). A1: Both points correctly found as \((-1, -4)\) and \((3.5, 0.5)\).
PastPaper.question 11 · Structured
11 PastPaper.marks
The quadratic equation \(2x^2 + 5x - 4 = 0\) has roots \(\alpha\) and \(\beta\). Without solving the equation: (a) Find the value of \(\alpha^2 + \beta^2\). (3 marks) (b) Find the value of \(\alpha^3 + \beta^3\). (3 marks) (c) Find a quadratic equation, with integer coefficients, which has roots \(\frac{\alpha}{\beta^2}\) and \(\frac{\beta}{\alpha^2}\). (5 marks)
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PastPaper.workedSolution

From the given equation, the sum and product of the roots are: \(\alpha + \beta = -\frac{5}{2}\) and \(\alpha\beta = -2\). (a) Using the identity: \(\alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha\beta = \left(-\frac{5}{2}\right)^2 - 2(-2) = \frac{25}{4} + 4 = \frac{41}{4}\). (b) Using the identity: \(\alpha^3 + \beta^3 = (\alpha + \beta)^3 - 3\alpha\beta(\alpha + \beta) = \left(-\frac{5}{2}\right)^3 - 3(-2)\left(-\frac{5}{2}\right) = -\frac{125}{8} - 15 = -\frac{245}{8}\). (c) The sum of the new roots is: \(S = \frac{\alpha}{\beta^2} + \frac{\beta}{\alpha^2} = \frac{\alpha^3 + \beta^3}{\alpha^2\beta^2} = \frac{-245/8}{(-2)^2} = \frac{-245/8}{4} = -\frac{245}{32}\). The product of the new roots is: \(P = \frac{\alpha}{\beta^2} \cdot \frac{\beta}{\alpha^2} = \frac{\alpha\beta}{\alpha^2\beta^2} = \frac{1}{\alpha\beta} = \frac{1}{-2} = -\frac{1}{2}\). The new quadratic equation is: \(x^2 - Sx + P = 0 \implies x^2 - \left(-\frac{245}{32}\right)x + \left(-\frac{1}{2}\right) = 0 \implies x^2 + \frac{245}{32}x - \frac{1}{2} = 0\). Multiplying by 32 to get integer coefficients yields: \(32x^2 + 245x - 16 = 0\).

PastPaper.markingScheme

(a) M1: Identifies \(\alpha+\beta = -2.5\) and \(\alpha\beta = -2\). M1: Employs identity \(\alpha^2+\beta^2 = (\alpha+\beta)^2 - 2\alpha\beta\). A1: Evaluates to obtain \(41/4\) (or \(10.25\)). (b) M1: Employs algebraic identity for sum of cubes. M1: Substitutes their values of sum and product. A1: Correctly evaluates to obtain \(-245/8\) (or \(-30.625\)). (c) M1: Expresses the sum of new roots in terms of \(\alpha\) and \(\beta\). A1: Evaluates the new sum to be \(-245/32\). M1: Expresses and evaluates the product of new roots as \(-1/2\). M1: Constructs quadratic equation using their sum and product. A1: Correct equation with integer coefficients (e.g. \(32x^2 + 245x - 16 = 0\)).

Paper 2R

Answer all questions. Calculators may be used. Show all stages in your working.
11 PastPaper.question · 99.79999999999998 PastPaper.marks
PastPaper.question 1 · Short Answer
5.2 PastPaper.marks
A solid sphere has volume \(V\text{ cm}^3\) and surface area \(A\text{ cm}^2\). The volume of the sphere is increasing at a constant rate of \(12\text{ cm}^3/\text{s}\). Find the rate of increase of the surface area, in \(\text{cm}^2/\text{s}\), at the instant when the radius of the sphere is \(4\text{ cm}\).
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PastPaper.workedSolution

We are given \(\frac{dV}{dt} = 12\).

The volume of a sphere is given by \(V = \frac{4}{3}\pi r^3\).

Differentiating with respect to \(r\):
\(\frac{dV}{dr} = 4\pi r^2\).

Using the chain rule, we can find \(\frac{dr}{dt}\):
\(\frac{dr}{dt} = \frac{dV}{dt} \div \frac{dV}{dr} = \frac{12}{4\pi r^2} = \frac{3}{\pi r^2}\).

The surface area of a sphere is given by \(A = 4\pi r^2\).

Differentiating with respect to \(r\):
\(\frac{dA}{dr} = 8\pi r\).

Using the chain rule to find \(\frac{dA}{dt}\):
\(\frac{dA}{dt} = \frac{dA}{dr} \times \frac{dr}{dt} = 8\pi r \times \frac{3}{\pi r^2} = \frac{24}{r}\).

At the instant when \(r = 4\):
\(\frac{dA}{dt} = \frac{24}{4} = 6\text{ cm}^2/\text{s}\).

PastPaper.markingScheme

M1: Attempts to differentiate \(V = \frac{4}{3}\pi r^3\) to find \(\frac{dV}{dr}\).
M1: Uses the chain rule to express \(\frac{dr}{dt}\) in terms of \(r\).
M1: Differentiates \(A = 4\pi r^2\) to find \(\frac{dA}{dr}\).
M1: Formulates a correct chain rule expression for \(\frac{dA}{dt}\), e.g. \(\frac{dA}{dt} = \frac{dA}{dr} \times \frac{dr}{dt}\).
A1.2: Correctly calculates \(\frac{dA}{dt} = 6\).
PastPaper.question 2 · Short Answer
5.2 PastPaper.marks
Find, to 1 decimal place, the values of \(\theta\) in the interval \(0^\circ \le \theta \le 360^\circ\) which satisfy the equation \(2\cos 2\theta - 5\sin\theta - 3 = 0\).
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PastPaper.workedSolution

Using the identity \(\cos 2\theta = 1 - 2\sin^2\theta\), we can rewrite the equation:
\(2(1 - 2\sin^2\theta) - 5\sin\theta - 3 = 0\)
\(2 - 4\sin^2\theta - 5\sin\theta - 3 = 0\)
\(-4\sin^2\theta - 5\sin\theta - 1 = 0\)

Multiply by \(-1\):
\(4\sin^2\theta + 5\sin\theta + 1 = 0\)

Factorize the quadratic equation:
\((4\sin\theta + 1)(\sin\theta + 1) = 0\)

This gives two cases:

Case 1: \(\sin\theta = -1\)
In the interval \(0^\circ \le \theta \le 360^\circ\), this gives \(\theta = 270^\circ\).

Case 2: \(\sin\theta = -0.25\)
The basic angle is \(\alpha = \arcsin(0.25) \approx 14.48^\circ\).
Since \(\sin\theta\) is negative, \(\theta\) lies in the 3rd and 4th quadrants:
\(\theta = 180^\circ + 14.48^\circ = 194.48^\circ \approx 194.5^\circ\) (to 1 d.p.)
\(\theta = 360^\circ - 14.48^\circ = 345.52^\circ \approx 345.5^\circ\) (to 1 d.p.).

Therefore, the solutions are \(\theta = 194.5^\circ, 270^\circ, 345.5^\circ\).

PastPaper.markingScheme

M1: Uses the double angle identity \(\cos 2\theta = 1 - 2\sin^2\theta\) to form a quadratic in \(\sin\theta\).
M1: Correctly factorizes or solves the quadratic equation \(4\sin^2\theta + 5\sin\theta + 1 = 0\) to obtain values for \(\sin\theta\).
A1: Identifies \(\theta = 270^\circ\).
M1: Uses \(\sin\theta = -0.25\) to find at least one correct quadrant angle.
A1.2: Both \(194.5^\circ\) and \(345.5^\circ\) correct (to 1 d.p.).
PastPaper.question 3 · Short Answer
5.2 PastPaper.marks
The sum to infinity of a geometric series is \(4.5\) times its second term. Given that the common ratio \(r\) of the series is positive, find the two possible values of \(r\).
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PastPaper.workedSolution

Let the first term of the geometric series be \(a\) and the common ratio be \(r\).
The sum to infinity is given by \(S_\infty = \frac{a}{1-r}\).
The second term is \(ar\).

According to the given condition:
\(\frac{a}{1-r} = 4.5 \times ar\)

Assuming \(a \ne 0\), we can divide both sides by \(a\):
\(\frac{1}{1-r} = \frac{9}{2}r\)

Multiply both sides by \(2(1-r)\):
\(2 = 9r(1-r)\)
\(2 = 9r - 9r^2\)

Rearranging into standard quadratic form:
\(9r^2 - 9r + 2 = 0\)

Factorizing the quadratic:
\((3r - 1)(3r - 2) = 0\)

This gives:
\(r = \frac{1}{3} or \)r = \frac{2}{3}\).

Both values are positive and satisfy \(|r| < 1\), so both are valid solutions.

PastPaper.markingScheme

M1: Sets up the equation \(\frac{a}{1-r} = 4.5ar\) using correct formulas for sum to infinity and the second term.
M1: Simplifies the equation by dividing by \(a\) to obtain an equation in terms of \(r\) only.
M1: Rearranges the equation to form a quadratic equation in standard form \(9r^2 - 9r + 2 = 0\).
M1: Solves the quadratic equation by factorization or formula.
A1.2: Obtains both \(r = \frac{1}{3} and \)r = \frac{2}{3}\).
PastPaper.question 4 · Short Answer
5.2 PastPaper.marks
The quadratic equation \(x^2 - 4px + (3p^2 + 4) = 0\), where \(p\) is a real constant, has real and distinct roots. Find the set of possible values of \(p\).
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PastPaper.workedSolution

For the quadratic equation to have real and distinct roots, its discriminant must be strictly greater than zero:
\(\Delta = b^2 - 4ac > 0\)

Here, \(a = 1\), \(b = -4p\), and \(c = 3p^2 + 4\).

Substitute these into the discriminant:
\((-4p)^2 - 4(1)(3p^2 + 4) > 0\)
\(16p^2 - 12p^2 - 16 > 0\)
\(4p^2 - 16 > 0\)

Divide by 4:
\(p^2 - 4 > 0\)
\(p^2 > 4\)

This inequality is satisfied when:
\(p > 2\) or \(p < -2\).

PastPaper.markingScheme

M1: Uses the condition for real and distinct roots, \(\Delta > 0\).
M1: Substitutes the coefficients into \(b^2 - 4ac\) to get an inequality in terms of \(p\).
A1: Simplifies the inequality to \(4p^2 - 16 > 0\) or equivalent.
M1: Solves the quadratic inequality \(p^2 - 4 > 0\) to find critical values \(2\) and \(-2\).
A1.2: Correctly expresses the final range as \(p < -2\) or \(p > 2\).
PastPaper.question 5 · Short Answer
5.2 PastPaper.marks
Solve the simultaneous equations: \(\log_2 x - 2\log_4 y = 1\) and \(3^x \cdot 9^y = 3^9\) where \(x > 0\) and \(y > 0\).
PastPaper.showAnswers

PastPaper.workedSolution

From the first equation:
\(\log_2 x - 2\log_4 y = 1\)

Using the change of base formula, \(\log_4 y = \frac{\log_2 y}{\log_2 4} = \frac{1}{2}\log_2 y\).
Substitute this back:
\(\log_2 x - 2\left(\frac{1}{2}\log_2 y\right) = 1\)
\(\log_2 x - \log_2 y = 1\)
\(\log_2\left(\frac{x}{y}\right) = 1\)
\(\frac{x}{y} = 2^1 \Rightarrow x = 2y\) (Equation 1)

From the second equation:
\(3^x \cdot 9^y = 3^9\)

Since \(9^y = (3^2)^y = 3^{2y}\):
\(3^x \cdot 3^{2y} = 3^9\)
\(3^{x + 2y} = 3^9\)

Equating exponents:
\(x + 2y = 9\) (Equation 2)

Substitute Equation 1 into Equation 2:
\(2y + 2y = 9\)
\(4y = 9 \Rightarrow y = 2.25\)

Using \(x = 2y\):
\(x = 2(2.25) = 4.5\).

Thus, the solution is \(x = 4.5, y = 2.25\).

PastPaper.markingScheme

M1: Applies the change of base formula to express \(\log_4 y\) in base 2.
M1: Simplifies the logarithmic equation to obtain \(x = 2y\).
M1: Uses index laws to rewrite the second equation as \(x + 2y = 9\).
M1: Solves the linear simultaneous equations.
A1.2: Obtains both \(x = 4.5\) and \(y = 2.25\).
PastPaper.question 6 · Structured/Multi-part
12.3 PastPaper.marks
(a) Show that \(\frac{\sin 3\theta}{\sin \theta} - \frac{\cos 3\theta}{\cos \theta} = 2\) for \(\theta \neq \frac{k\pi}{2}\), where \(k\) is an integer. (b) Hence, or otherwise, solve the equation \(\frac{\sin 3\theta}{\sin \theta} - \frac{\cos 3\theta}{\cos \theta} = 4\cos^2 \theta - 1\) for \(0^\circ \le \theta \le 180^\circ\).
PastPaper.showAnswers

PastPaper.workedSolution

(a) Start with LHS: \(\frac{\sin 3\theta}{\sin \theta} - \frac{\cos 3\theta}{\cos \theta} = \frac{\sin 3\theta \cos \theta - \cos 3\theta \sin \theta}{\sin \theta \cos \theta}\). Using the compound angle identity \(\sin(A - B) = \sin A \cos B - \cos A \sin B\), the numerator becomes: \(\sin 3\theta \cos \theta - \cos 3\theta \sin \theta = \sin(3\theta - \theta) = \sin 2\theta\). Using the double angle identity \(\sin 2\theta = 2\sin\theta\cos\theta\), we get: \(\frac{\sin 2\theta}{\sin\theta\cos\theta} = \frac{2\sin\theta\cos\theta}{\sin\theta\cos\theta} = 2\). (b) The equation simplifies to: \(2 = 4\cos^2\theta - 1\), which gives \(4\cos^2\theta = 3\), so \\cos^2\theta = \frac{3}{4}\) and \(\cos\theta = \pm\frac{\sqrt{3}}{2}\). For \(0^\circ \le \theta \le 180^\circ\), the solutions are: if \(\cos\theta = \frac{\sqrt{3}}{2}\), then \(\theta = 30^\circ\); if \(\cos\theta = -\frac{\sqrt{3}}{2}\), then \(\theta = 150^\circ\). Both values are within the range and do not make \(\sin\theta = 0\) or \(\cos\theta = 0\).

PastPaper.markingScheme

(a) M1: Attempts to write as a single fraction with a common denominator. M1: Uses the sine compound angle formula correctly on the numerator. M1: Uses the double angle formula for \(\sin 2\theta\). A1: Completes the proof to reach 2. (b) M1: Equates the simplified LHS to the RHS to get \(2 = 4\cos^2\theta - 1\). M1: Rearranges to make \(\cos^2\theta\) or \(\cos\theta\) the subject. A1: Obtains \(\cos\theta = \pm\frac{\sqrt{3}}{2}\). M1: Finds one correct principal value for \(\theta\). A1: Obtains both \(\theta = 30^\circ\) and \(\theta = 150^\circ\) (and no extra values in range).
PastPaper.question 7 · Structured/Multi-part
12.3 PastPaper.marks
The curve \(C\) has equation \(y = e^x \sqrt{2x + 1}\) for \(x > -0.5\). (a) Show that \(\frac{\text{d}y}{\text{d}x} = \frac{2e^x(x + 1)}{\sqrt{2x + 1}}\). (b) The region \(R\) is bounded by the curve \(C\), the \(x\)-axis, and the lines \(x = 0\) and \(x = 1\). Find the exact volume of the solid generated when \(R\) is rotated through \(360^\circ\) about the \(x\)-axis.
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PastPaper.workedSolution

(a) Applying the product rule to \(y = e^x (2x + 1)^{\frac{1}{2}}\): \(\frac{\text{d}y}{\text{d}x} = e^x (2x+1)^{\frac{1}{2}} + e^x \cdot \frac{1}{2}(2x+1)^{-\frac{1}{2}} \cdot 2 = e^x (2x+1)^{\frac{1}{2}} + e^x (2x+1)^{-\frac{1}{2}}\). Factoring out \(e^x (2x+1)^{-\frac{1}{2}}\): \(\frac{\text{d}y}{\text{d}x} = e^x (2x+1)^{-\frac{1}{2}} ((2x+1) + 1) = \frac{2e^x(x+1)}{\sqrt{2x+1}}\). (b) The volume of revolution is \(V = \pi \int_{0}^{1} y^2 \text{d}x = \pi \int_{0}^{1} (2x + 1)e^{2x} \text{d}x\). Using integration by parts with \(u = 2x+1\) and \(\text{d}v = e^{2x} \text{d}x\), we get \(\int (2x+1)e^{2x} \text{d}x = (2x+1)\frac{e^{2x}}{2} - \int e^{2x} \text{d}x = \frac{2x+1}{2}e^{2x} - \frac{1}{2}e^{2x} = xe^{2x}\). Evaluating between the limits 0 and 1: \(V = \pi [xe^{2x}]_{0}^{1} = \pi (1e^2 - 0) = \pi e^2\).

PastPaper.markingScheme

(a) M1: Applies the product rule or quotient rule to differentiate \(y\). A1: Correctly differentiates \((2x+1)^{\frac{1}{2}}\) to get \(\frac{1}{\sqrt{2x+1}}\). M1: Attempts to put terms over a common denominator. A1: Obtains the correct given expression showing all steps. (b) M1: Uses the volume formula \(V = \pi \int y^2 \text{d}x\) with limits 0 and 1. A1: Correctly writes the integrand as \((2x + 1)e^{2x}\). M1: Applies integration by parts with correct choice of \(u\) and \(\text{d}v\). A1: Obtains \(xe^{2x}\) as the integral. M1: Substitutes limits 1 and 0 into their integrated expression. A1: Final answer of \(\pi e^2\) (must be exact).
PastPaper.question 8 · Structured/Multi-part
12.3 PastPaper.marks
An arithmetic progression \(A\) has first term \(a\) and common difference \(d\), where \(d \neq 0\). A geometric progression \(G\) has first term \(a\) and common ratio \(r\). The 1st, 3rd, and 7th terms of \(A\) are equal to the first three terms of \(G\) respectively. (a) Show that \(d = \frac{1}{2}a\) and find the value of \(r\). (b) Given also that the sum of the first 10 terms of \(A\) is 130: (i) find the value of \(a\), (ii) find the sum of the first 8 terms of \(G\).
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PastPaper.workedSolution

(a) The terms are \(u_1 = a\), \(u_3 = a + 2d\), and \(u_7 = a + 6d\). Since these form a GP, \(\frac{a + 2d}{a} = \frac{a + 6d}{a + 2d}\), so \((a + 2d)^2 = a(a + 6d)\). This simplifies to \(a^2 + 4ad + 4d^2 = a^2 + 6ad\), which yields \(4d^2 - 2ad = 0\). Since \(d \neq 0\), we divide by \(2d\) to get \(2d - a = 0 \implies d = \frac{1}{2}a\). The common ratio is \(r = \frac{a+2d}{a} = \frac{a+a}{a} = 2\). (b)(i) The sum of the first 10 terms of \(A\) is \(S_{10} = 5(2a + 9d) = 130\). Substituting \(d = \frac{1}{2}a\): \(5(2a + 4.5a) = 130 \implies 32.5a = 130 \implies a = 4\). (ii) The first term of \(G\) is \(a = 4\) and the common ratio is \(r = 2\). The sum of the first 8 terms of \(G\) is \(S_8 = \frac{4(2^8 - 1)}{2 - 1} = 4(255) = 1020\).

PastPaper.markingScheme

(a) M1: Writes expressions for terms of \(A\) in terms of \(a\) and \(d\). M1: Sets up the geometric progression condition. A1: Correctly simplifies and solves to show \(d = \frac{1}{2}a\). A1: Deduces that \(r = 2\). (b)(i) M1: Uses the sum formula for an AP with \(n=10\) set to 130. M1: Substitutes \(d = \frac{1}{2}a\). A1: Solves to find \(a = 4\). (b)(ii) M1: Uses the geometric series sum formula with \(n=8\). A1: Obtains 1020.
PastPaper.question 9 · Structured/Multi-part
12.3 PastPaper.marks
In triangle \(OAB\), \(\overrightarrow{OA} = \mathbf{a}\) and \(\overrightarrow{OB} = \mathbf{b}\). The point \(P\) lies on \(OA\) such that \(OP : PA = 2 : 1\). The point \(Q\) lies on \(OB\) such that \(OQ : QB = 1 : 3\). The lines \(AQ\) and \(BP\) intersect at the point \(X\). (a) Express \(\overrightarrow{AQ}\) and \(\overrightarrow{BP}\) in terms of \(\mathbf{a}\) and \(\mathbf{b}\). (b) Using a vector method, find \(\overrightarrow{OX}\) in terms of \(\mathbf{a}\) and \(\mathbf{b}\). (c) Find the ratio \(AX : XQ\).
PastPaper.showAnswers

PastPaper.workedSolution

(a) Since \(OP : PA = 2 : 1\), \(\overrightarrow{OP} = \frac{2}{3}\mathbf{a}\). Since \(OQ : QB = 1 : 3\), \(\overrightarrow{OQ} = \frac{1}{4}\mathbf{b}\). Therefore, \(\overrightarrow{AQ} = \overrightarrow{AO} + \overrightarrow{OQ} = -\mathbf{a} + \frac{1}{4}\mathbf{b}\) and \(\overrightarrow{BP} = \overrightarrow{BO} + \overrightarrow{OP} = \frac{2}{3}\mathbf{a} - \mathbf{b}\). (b) Since \(X\) lies on \(AQ\), \(\overrightarrow{OX} = \mathbf{a} + \lambda \overrightarrow{AQ} = (1 - \lambda)\mathbf{a} + \frac{1}{4}\lambda\mathbf{b}\). Since \(X\) also lies on \(BP\), \(\overrightarrow{OX} = \mathbf{b} + \mu \overrightarrow{BP} = \frac{2}{3}\mu\mathbf{a} + (1 - \mu)\mathbf{b}\). Equating coefficients of \(\mathbf{a}\) and \(\mathbf{b}\): \(1 - \lambda = \frac{2}{3}\mu\) and \(\frac{1}{4}\lambda = 1 - \mu\). Solving these simultaneous equations gives \(\lambda = \frac{2}{5}\) and \(\mu = \frac{9}{10}\). Substituting \(\lambda = \frac{2}{5}\) back gives \(\overrightarrow{OX} = \frac{3}{5}\mathbf{a} + \frac{1}{10}\mathbf{b}\). (c) Since \(\overrightarrow{AX} = \lambda \overrightarrow{AQ} = \frac{2}{5}\overrightarrow{AQ}\), then \(\overrightarrow{XQ} = \frac{3}{5}\overrightarrow{AQ}\). Thus, the ratio \(AX : XQ = 2 : 3\).

PastPaper.markingScheme

(a) M1: Finds \(\overrightarrow{OP}\) and \(\overrightarrow{OQ}\) in terms of vectors. A1: Obtains correct expressions for \(\overrightarrow{AQ}\) and \(\overrightarrow{BP}\). (b) M1: Expresses \(\overrightarrow{OX}\) in two different ways using scalar parameters. M1: Equates coefficients of \(\mathbf{a}\) and \(\mathbf{b}\) to set up simultaneous equations. A1: Solves to find a parameter correctly. A1: Obtains the correct vector \(\overrightarrow{OX}\). (c) M1: Relates the ratio to the parameter \(\lambda\). A1: Deduces the ratio \(2 : 3\).
PastPaper.question 10 · Structured/Multi-part
12.3 PastPaper.marks
The points \(A\) and \(B\) have coordinates \((1, 3)\) and \((5, 11)\) respectively. (a) Find the equation of the perpendicular bisector of \(AB\), giving your answer in the form \(ay + bx + c = 0\), where \(a\), \(b\), and \(c\) are integers. (b) The perpendicular bisector of \(AB\) meets the \(y\)-axis at the point \(C\). Find the coordinates of \(C\). (c) Find the area of triangle \(ABC\).
PastPaper.showAnswers

PastPaper.workedSolution

(a) The midpoint \(M\) of \(AB\) is \((\frac{1+5}{2}, \frac{3+11}{2}) = (3, 7)\). The gradient of \(AB\) is \(m = \frac{11 - 3}{5 - 1} = 2\). The gradient of the perpendicular bisector is \(m_{\perp} = -\frac{1}{2}\). The equation is \(y - 7 = -\frac{1}{2}(x - 3) \implies 2y - 14 = -x + 3 \implies 2y + x - 17 = 0\). (b) Setting \(x = 0\) in the equation of the line: \(2y - 17 = 0 \implies y = 8.5\), so \(C = (0, 8.5)\). (c) Using the coordinates \(A(1, 3)\), \(B(5, 11)\), and \(C(0, 8.5)\) in the area formula: \(\text{Area} = \frac{1}{2} |1(11 - 8.5) + 5(8.5 - 3) + 0(3 - 11)| = \frac{1}{2} |2.5 + 27.5| = 15\).

PastPaper.markingScheme

(a) M1: Finds the midpoint of \(AB\). M1: Finds the gradient of \(AB\) and uses it to find the perpendicular gradient. M1: Writes down the equation of the line using their midpoint and perpendicular gradient. A1: Obtains \(2y + x - 17 = 0\) or integer multiple. (b) B1: Correctly substitutes \(x=0\) to find \(C(0, 8.5)\). (c) M1: Applies a valid method to find the area of a triangle given three vertices. M1: Substitutes coordinates correctly. A1: Obtains 15.
PastPaper.question 11 · Structured/Multi-part
12.3 PastPaper.marks
Let \(f(x) = \frac{2x - 3}{x + 1}\) for \(x \neq -1\). (a) State the equations of the asymptotes to the curve with equation \(y = f(x)\). (b) Find the coordinates of the points where the curve crosses the coordinate axes. (c) Sketch the curve \(y = f(x)\), showing clearly the asymptotes and the coordinates of the points of intersection with the axes. (d) By drawing a suitable straight line on your sketch, or otherwise, solve the inequality \(\frac{2x - 3}{x + 1} \le x - 3\).
PastPaper.showAnswers

PastPaper.workedSolution

(a) The vertical asymptote is when the denominator is zero: \(x = -1\). The horizontal asymptote is \(y = \lim_{x \to \pm\infty} f(x) = 2\). (b) For \(y = 0\), \(2x - 3 = 0 \implies x = 1.5\), giving \((1.5, 0)\). For \(x = 0\), \(y = -3\), giving \((0, -3)\). (c) The sketch should show a rectangular hyperbola with branches in the upper-left and lower-right regions defined by the asymptotes \(x = -1\) and \(y = 2\), passing through the axes at \((1.5, 0)\) and \((0, -3)\). (d) The line is \(y = x - 3\). To find the intersections, set \(\frac{2x - 3}{x + 1} = x - 3 \implies 2x - 3 = x^2 - 2x - 3 \implies x^2 - 4x = 0\), giving \(x = 0\) and \(x = 4\). From the sketch, the curve lies below or on the line when \(-1 < x \le 0\) or \(x \ge 4\).

PastPaper.markingScheme

(a) B1: Correct vertical asymptote \(x = -1\). B1: Correct horizontal asymptote \(y = 2\). (b) B1: Both coordinates \((1.5, 0)\) and \((0, -3)\) correct. (c) B1: Correct shape with two branches. B1: Both asymptotes drawn and labeled. B1: Axes intercepts correctly shown. (d) M1: Solves \(\frac{2x - 3}{x + 1} = x - 3\). A1: Finds intersection coordinates \(x = 0\) and \(x = 4\). M1: Identifies intervals graphically or algebraically. A1: Obtains \(-1 < x \le 0\) or \(x \ge 4\).

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