If any of my solutions look wrong, please refer to the mark scheme. You can exit full-screen mode for the question paper and mark scheme by clicking the icon in the bottom-right corner or by pressing Esc on your keyboard.
AQA Level 2 Further Maths Paper 1 (Non-Calculator) 2024
๐ Guidance
- Paper Type: Non-Calculator (Show all working clearly)
- Total Questions: 23
- Format: Interactive Worksheets with Pedagogical Solutions
- Notation: Standard MathJax \( x^2 \) notation used throughout
๐ Table of Contents
- Question 1 (Surds & Standard Form)
- Question 2 (Factorisation)
- Question 3 (Limits of Sequences)
- Question 4 (Coordinate Geometry)
- Question 5 (Differentiation)
- Question 6 (Circle Geometry)
- Question 7 (Matrices)
- Question 8 (Cubic Equations)
- Question 9 (3D Pythagoras)
- Question 10 (Functions & Graphs)
- Question 11 (Factor Theorem)
- Question 12 (Trigonometry)
- Question 13 (Inequalities)
- Question 14 (Completing the Square)
- Question 15 (Matrix Transformations)
- Question 16 (Circle Theorems)
- Question 17 (Algebraic Fractions)
- Question 18 (Surds Rationalisation)
- Question 19 (Stationary Points)
- Question 20 (Graphical Solutions)
- Question 21 (Indices)
- Question 22 (Trigonometric Identities)
- Question 23 (Quadratic Sequences)
Question 1 (2 marks)
Work out the value of \( \sqrt{\frac{t}{20}} \) where \( t = 2.42 \times 10^3 \)
๐ Worked Solution
Step 1: Convert standard form to an ordinary number
๐ก Why we do this: Working with ordinary integers is often easier for division than working with standard form directly, especially when we need to find a square root later.
โ Working:
\[ t = 2.42 \times 1000 = 2420 \]Step 2: Substitute and simplify the fraction
๐ก Strategy: Place the value of \( t \) into the expression and perform the division before taking the square root.
โ Working:
\[ \frac{t}{20} = \frac{2420}{20} \]Cancel the zeros:
\[ \frac{242}{2} = 121 \]Step 3: Calculate the square root
๐ก Verification: We recognize 121 as a square number.
โ Working:
\[ \sqrt{121} = 11 \]โ (M1 for 121, A1 for 11)
๐ Final Answer:
11
Question 2 (1 mark)
Factorise \( x^2 – y^2 \)
๐ Worked Solution
Step 1: Identify the algebraic structure
๐ก What this tells us: This is a standard identity known as the “Difference of Two Squares”. It always follows the pattern \( a^2 – b^2 = (a-b)(a+b) \).
โ Working:
\[ x^2 – y^2 = (x – y)(x + y) \]โ (B1)
๐ Final Answer:
\( (x – y)(x + y) \)
Question 3 (1 mark)
The \( n \)th term of a sequence is \( \frac{3n + 4}{n} \)
Circle the limiting value of \( \frac{3n + 4}{n} \) as \( n \to \infty \)
1 3 4 7
๐ Worked Solution
Step 1: Simplify the expression
๐ก Why we do this: To see what happens as \( n \) gets very large, it helps to split the fraction into separate terms.
โ Working:
\[ \frac{3n + 4}{n} = \frac{3n}{n} + \frac{4}{n} = 3 + \frac{4}{n} \]Step 2: Apply the limit
๐ก What this tells us: As \( n \) becomes infinitely large (\( n \to \infty \)), the fraction \( \frac{4}{n} \) becomes closer and closer to 0.
โ Working:
\[ \text{Limit} = 3 + 0 = 3 \]โ (B1)
๐ Final Answer:
3
Question 4 (2 marks)
The equations of two straight lines are
\( y – 3x = 4 \) and \( 6y = 18x – 5 \)
Show that the lines are parallel.
๐ Worked Solution
Step 1: Understand the condition for parallel lines
๐ก Core Principle: Parallel lines must have the same gradient (\( m \)). To find the gradient, we rearrange both equations into the form \( y = mx + c \).
Step 2: Rearrange the first equation
โ Working:
\[ y – 3x = 4 \] \[ y = 3x + 4 \]Gradient \( m_1 = 3 \)
Step 3: Rearrange the second equation
โ Working:
\[ 6y = 18x – 5 \]Divide all terms by 6:
\[ y = \frac{18}{6}x – \frac{5}{6} \] \[ y = 3x – \frac{5}{6} \]Gradient \( m_2 = 3 \)
Step 4: Conclusion
โ Working:
Since \( m_1 = 3 \) and \( m_2 = 3 \), the gradients are equal.
Therefore, the lines are parallel.
โ (M1 for rearranging, A1 for conclusion)
๐ Final Answer:
Both gradients are 3, so lines are parallel.
Question 5 (3 marks)
\( y = \frac{4x^3 + x^7}{x^4} \)
Work out \( \frac{dy}{dx} \)
๐ Worked Solution
Step 1: Simplify the expression before differentiating
๐ก Strategy: It is much easier to differentiate separate terms of the form \( ax^n \) than a fraction. We divide each term in the numerator by \( x^4 \).
โ Working:
\[ y = \frac{4x^3}{x^4} + \frac{x^7}{x^4} \] \[ y = 4x^{-1} + x^3 \]โ (M1 for correct term simplified)
Step 2: Differentiate term by term
๐ก How: Use the power rule: multiply by the power, reduce the power by 1.
- For \( 4x^{-1} \): \( -1 \times 4x^{-2} = -4x^{-2} \)
- For \( x^3 \): \( 3 \times x^2 = 3x^2 \)
โ Working:
\[ \frac{dy}{dx} = -4x^{-2} + 3x^2 \]โ (A1 for one term correct, A1 for both)
๐ Final Answer:
\( \frac{dy}{dx} = -4x^{-2} + 3x^2 \) or \( -\frac{4}{x^2} + 3x^2 \)
Question 6 (3 marks)
Points \( A(-12, 1) \) and \( B(12, -1) \) lie on a circle.
\( AB \) is a diameter of the circle.
Work out the equation of the circle.
๐ Worked Solution
Step 1: Find the centre of the circle
๐ก Why we do this: The centre of the circle is the midpoint of the diameter \( AB \).
โ Working:
\[ \text{Centre} = \left( \frac{x_1 + x_2}{2}, \frac{y_1 + y_2}{2} \right) \] \[ \text{Centre} = \left( \frac{-12 + 12}{2}, \frac{1 + (-1)}{2} \right) \] \[ \text{Centre} = (0, 0) \]โ (B1)
Step 2: Find the radius squared (\( r^2 \))
๐ก How: The radius is the distance from the centre (0,0) to point A (or B). We use Pythagoras’ theorem.
โ Working:
\[ r^2 = (x – 0)^2 + (y – 0)^2 \]Using point A(-12, 1):
\[ r^2 = (-12)^2 + 1^2 \] \[ r^2 = 144 + 1 = 145 \]โ (M1)
Step 3: Write the equation
๐ก Formula: The equation of a circle with centre (0,0) is \( x^2 + y^2 = r^2 \).
โ Working:
\[ x^2 + y^2 = 145 \]โ (B1)
๐ Final Answer:
\( x^2 + y^2 = 145 \)
Question 7 (3 marks)
A point \( P(x, y) \) is transformed using the transformation represented by \( \begin{pmatrix} 4 & 0 \\ -2 & 3 \end{pmatrix} \)
The image of \( P \) is \( (-8, 7) \)
Work out the values of \( x \) and \( y \).
๐ Worked Solution
Step 1: Set up the matrix multiplication
๐ก What this tells us: Multiplying the matrix by the point vector gives the image vector.
โ Working:
\[ \begin{pmatrix} 4 & 0 \\ -2 & 3 \end{pmatrix} \begin{pmatrix} x \\ y \end{pmatrix} = \begin{pmatrix} -8 \\ 7 \end{pmatrix} \]โ (M1)
Step 2: Form equations from rows
โ Working:
Top row: \( 4x + 0y = -8 \)
Bottom row: \( -2x + 3y = 7 \)
โ (M1)
Step 3: Solve the equations
โ Working:
From top row:
\[ 4x = -8 \implies x = -2 \]Substitute \( x = -2 \) into bottom row:
\[ -2(-2) + 3y = 7 \] \[ 4 + 3y = 7 \] \[ 3y = 3 \implies y = 1 \]โ (A1)
๐ Final Answer:
\( x = -2, \quad y = 1 \)
Question 8 (3 marks)
Solve by factorising \( 2x^3 – 9x^2 – 5x = 0 \)
๐ Worked Solution
Step 1: Factor out the common term \( x \)
๐ก Strategy: Always check for a common factor first. Here, every term contains \( x \).
โ Working:
\[ x(2x^2 – 9x – 5) = 0 \]โ (M1)
Step 2: Factorise the quadratic part
๐ก How: We need to factorise \( 2x^2 – 9x – 5 \). We need numbers that multiply to \( 2 \times -5 = -10 \) and add to \( -9 \). These are \( -10 \) and \( 1 \).
โ Working:
\[ 2x^2 – 10x + x – 5 \] \[ 2x(x – 5) + 1(x – 5) \] \[ (2x + 1)(x – 5) \]So the full equation is:
\[ x(2x + 1)(x – 5) = 0 \]โ (M1)
Step 3: Find the solutions
๐ก Check: Set each bracket to zero.
โ Working:
\( x = 0 \)
\( 2x + 1 = 0 \implies x = -0.5 \)
\( x – 5 = 0 \implies x = 5 \)
โ (A1)
๐ Final Answer:
\( x = 0, \quad x = -0.5, \quad x = 5 \)
Question 9 (3 marks)
\( ABCDEFGH \) is a cuboid.
Work out the length \( AG \).
๐ Worked Solution
Step 1: Identify the method (3D Pythagoras)
๐ก Core Principle: To find the space diagonal \( AG \) of a cuboid, we use the 3D Pythagoras formula: \( d = \sqrt{x^2 + y^2 + z^2} \).
Step 2: Substitute the dimensions
โ Working:
Length = 4 cm, Width = 3 cm, Height = 12 cm
\[ AG = \sqrt{4^2 + 3^2 + 12^2} \] \[ AG = \sqrt{16 + 9 + 144} \]โ (M1)
Step 3: Calculate the result
โ Working:
\[ AG = \sqrt{169} \] \[ AG = 13 \]โ (M1 for 169, A1 for 13)
๐ Final Answer:
13 cm
Question 10 (5 marks)
A function \( f \) is given by
\( f(x) = -\frac{1}{2}x + 21 \quad \text{for } 0 \le x \le 2 \)
\( f(x) = ax^2 + bx \quad \text{for } 2 < x \le 6 \)
A sketch of \( y = f(x) \) is shown.
Work out the values of \( a \) and \( b \).
๐ Worked Solution
Step 1: Find the coordinates of P
๐ก Analysis: Point P is at \( x = 2 \). Since the function is continuous, the value of the first part \( f(x) = -\frac{1}{2}x + 21 \) at \( x=2 \) gives the y-coordinate of P.
โ Working:
\[ y = -\frac{1}{2}(2) + 21 \] \[ y = -1 + 21 = 20 \]So P is \( (2, 20) \).
โ (M1 for P coordinates)
Step 2: Set up equations for \( a \) and \( b \)
๐ก Strategy: The quadratic part \( f(x) = ax^2 + bx \) passes through P(2, 20) and Q(6, 12). We form two simultaneous equations.
โ Working:
At P(2, 20):
\[ a(2)^2 + b(2) = 20 \] \[ 4a + 2b = 20 \quad \text{(Divide by 2)} \rightarrow \quad 2a + b = 10 \quad \text{(1)} \]At Q(6, 12):
\[ a(6)^2 + b(6) = 12 \] \[ 36a + 6b = 12 \quad \text{(Divide by 6)} \rightarrow \quad 6a + b = 2 \quad \text{(2)} \]โ (M1, M1)
Step 3: Solve the simultaneous equations
โ Working:
Subtract equation (1) from equation (2):
\[ (6a + b) – (2a + b) = 2 – 10 \] \[ 4a = -8 \] \[ a = -2 \]Substitute \( a = -2 \) into equation (1):
\[ 2(-2) + b = 10 \] \[ -4 + b = 10 \] \[ b = 14 \]โ (A1, A1)
๐ Final Answer:
\( a = -2, \quad b = 14 \)
Question 11 (6 marks)
(a) \( (3x – 7) \) is a factor of \( 3x^3 – 4x^2 – 13x + 14 \)
Work out the other two linear factors.
(b) \( (x – 2) \) is a factor of \( ax^4 – 3ax^3 + 5x – 22 \)
Work out the value of \( a \).
๐ Worked Solution
Part (a): Polynomial Division
๐ก Strategy: Since \( (3x-7) \) is a factor, we can divide the cubic by it to find the remaining quadratic factor.
โ Working:
Compare coefficients or use division:
\[ (3x – 7)(Ax^2 + Bx + C) = 3x^3 – 4x^2 – 13x + 14 \]- \( 3x \times Ax^2 = 3x^3 \implies A = 1 \)
- \( -7 \times C = 14 \implies C = -2 \)
Checking \( x^2 \) term: \( (3x)(Bx) + (-7)(x^2) = -4x^2 \)
\[ 3B – 7 = -4 \] \[ 3B = 3 \implies B = 1 \]The quadratic factor is \( x^2 + x – 2 \).
โ (M1)
Part (a): Factorise the quadratic
โ Working:
\[ x^2 + x – 2 = (x + 2)(x – 1) \]โ (A1)
Part (b): Factor Theorem
๐ก Core Principle: If \( (x – 2) \) is a factor, then substituting \( x = 2 \) into the polynomial must give 0.
โ Working:
\[ f(2) = 0 \] \[ a(2)^4 – 3a(2)^3 + 5(2) – 22 = 0 \] \[ 16a – 3a(8) + 10 – 22 = 0 \] \[ 16a – 24a – 12 = 0 \] \[ -8a = 12 \] \[ a = \frac{12}{-8} = -1.5 \]โ (M1, M1, A1)
๐ Final Answer:
(a) \( (x+2) \) and \( (x-1) \)
(b) \( a = -1.5 \)
Question 12 (3 marks)
In triangle \( ABC \), \( \cos A = \frac{3}{4} \)
Work out the length \( BC \).
๐ Worked Solution
Step 1: Identify the rule
๐ก Strategy: We have two sides and the included angle (or its cosine). This is a job for the Cosine Rule: \( a^2 = b^2 + c^2 – 2bc \cos A \).
Step 2: Substitute values
โ Working:
\[ BC^2 = 12^2 + 10^2 – 2(12)(10)\left(\frac{3}{4}\right) \] \[ BC^2 = 144 + 100 – 240\left(\frac{3}{4}\right) \]โ (M1)
Step 3: Calculate
โ Working:
\[ 240 \div 4 = 60 \implies 60 \times 3 = 180 \] \[ BC^2 = 244 – 180 \] \[ BC^2 = 64 \] \[ BC = \sqrt{64} = 8 \]โ (M1, A1)
๐ Final Answer:
8 cm
Question 13 (4 marks)
A garden patio is made from two rectangles. All lengths are in metres.
The area of the patio is less than 51 mยฒ.
Work out the range of possible values of \( x \).
Give your answer in the form \( a < x < b \) where \( a \) and \( b \) are both integers.
๐ Worked Solution
Step 1: Express the area in terms of x
๐ก Strategy: Split the L-shape into two rectangles. We can split it vertically.
- Rectangle 1 (Left): Width 7, Height \( x \). Area = \( 7x \).
- Rectangle 2 (Right): Width 8, Height \( x – 3 \). Area = \( 8(x-3) \).
โ Working:
\[ \text{Total Area} = 7x + 8(x – 3) \] \[ = 7x + 8x – 24 \] \[ = 15x – 24 \]โ (M1)
Step 2: Form and solve the inequality
โ Working:
\[ 15x – 24 < 51 \] \[ 15x < 75 \] \[ x < 5 \]โ (M1)
Step 3: Consider geometric constraints
๐ก Critical Check: A length cannot be zero or negative. The shortest vertical side is \( x – 3 \).
โ Working:
\[ x – 3 > 0 \] \[ x > 3 \]โ (B1)
๐ Final Answer:
\( 3 < x < 5 \)
Question 14 (4 marks)
(a) Write \( 2x^2 – 16x + 7 \) in the form \( k(x + m)^2 + n \) where \( k, m \) and \( n \) are integers.
(b) Solve \( (x – 1)^2 – 5 = 0 \)
๐ Worked Solution
Part (a): Completing the Square
๐ก Strategy: Factor out the coefficient of \( x^2 \) from the first two terms first.
โ Working:
\[ 2(x^2 – 8x) + 7 \]Complete the square for \( x^2 – 8x \): \( (x-4)^2 – 16 \)
\[ 2[(x – 4)^2 – 16] + 7 \] \[ 2(x – 4)^2 – 32 + 7 \] \[ 2(x – 4)^2 – 25 \]โ (M1, M1, A1)
Part (b): Solving
โ Working:
\[ (x – 1)^2 = 5 \] \[ x – 1 = \pm\sqrt{5} \] \[ x = 1 \pm \sqrt{5} \]โ (B1)
๐ Final Answer:
(a) \( 2(x – 4)^2 – 25 \)
(b) \( 1 \pm \sqrt{5} \)
Question 15 (3 marks)
(a) Matrix \( M \) represents a reflection in the line \( y = -x \)
Write down matrix \( M \)
(b) \( N = \begin{pmatrix} 0 & 1 \\ -1 & 0 \end{pmatrix} \)
Describe geometrically the single transformation represented by \( N^2 \)
๐ Worked Solution
Part (a): Reflection Matrix
๐ก Analysis: The line \( y = -x \) swaps coordinates and changes signs. \( (1, 0) \to (0, -1) \) and \( (0, 1) \to (-1, 0) \).
โ Working:
\[ M = \begin{pmatrix} 0 & -1 \\ -1 & 0 \end{pmatrix} \]โ (B1)
Part (b): Calculate \( N^2 \)
โ Working:
\[ N^2 = \begin{pmatrix} 0 & 1 \\ -1 & 0 \end{pmatrix} \begin{pmatrix} 0 & 1 \\ -1 & 0 \end{pmatrix} \] \[ = \begin{pmatrix} (0)(0) + (1)(-1) & (0)(1) + (1)(0) \\ (-1)(0) + (0)(-1) & (-1)(1) + (0)(0) \end{pmatrix} \] \[ = \begin{pmatrix} -1 & 0 \\ 0 & -1 \end{pmatrix} \]โ (M1)
Part (b): Describe Transformation
๐ก Interpretation: The matrix \( \begin{pmatrix} -1 & 0 \\ 0 & -1 \end{pmatrix} \) changes the sign of both x and y. This corresponds to a 180ยฐ rotation.
โ Working:
Rotation 180ยฐ about the origin (or enlargement scale factor -1).
โ (A1)
๐ Final Answer:
(a) \( \begin{pmatrix} 0 & -1 \\ -1 & 0 \end{pmatrix} \)
(b) Rotation 180ยฐ about the origin
Question 16 (4 marks)
\( A, B, C \) and \( D \) are points on a circle, centre \( O \).
Angle \( OBC \) : Angle \( ODC = 5 : 3 \)
Work out the size of angle \( OBC \).
You must show your working.
๐ Worked Solution
Step 1: Use Circle Theorems
๐ก Strategy: We need to find the angles in the quadrilateral.
1. Since \( ABCD \) is a cyclic quadrilateral, opposite angles add to 180ยฐ.
2. Angle at centre is double the angle at the circumference.
โ Working:
Angle \( BCD = 180ยฐ – 52ยฐ = 128ยฐ \)
Step 2: Set up algebraic expression for angles
๐ก Insight: \( OB \) and \( OD \) are radii, so triangles \( OBC \) and \( ODC \) are isosceles. This means angle \( OCB = \) angle \( OBC \) and angle \( OCD = \) angle \( ODC \).
The question gives the ratio \( OBC : ODC = 5 : 3 \). Let’s use \( x \).
โ Working:
Let Angle \( OBC = 5x \)
Let Angle \( ODC = 3x \)
Therefore, Angle \( OCB = 5x \) and Angle \( OCD = 3x \).
The total angle \( BCD \) is the sum of these:
\[ 5x + 3x = 128 \] \[ 8x = 128 \]โ (M1)
Step 3: Solve for angle OBC
โ Working:
\[ x = \frac{128}{8} = 16 \]We need Angle \( OBC \) which is \( 5x \):
\[ 5 \times 16 = 80^{\circ} \]โ (A1)
๐ Final Answer:
80ยฐ
Question 17 (3 marks)
Show that \( \frac{21x}{3x^2 – 2x – 8} – \frac{7}{x – 2} \) simplifies to \( \frac{k}{3x^2 – 2x – 8} \)
where \( k \) is an integer.
๐ Worked Solution
Step 1: Factorise the denominator
๐ก Strategy: To subtract fractions, we need a common denominator. Let’s factorise \( 3x^2 – 2x – 8 \) first.
โ Working:
We need numbers that multiply to \( 3 \times -8 = -24 \) and add to \( -2 \). (-6 and 4).
\[ 3x^2 – 6x + 4x – 8 \] \[ 3x(x – 2) + 4(x – 2) \] \[ (3x + 4)(x – 2) \]โ (M1)
Step 2: Convert to common denominator
โ Working:
The expression becomes:
\[ \frac{21x}{(3x + 4)(x – 2)} – \frac{7}{x – 2} \]Multiply top and bottom of the second fraction by \( (3x + 4) \):
\[ \frac{21x}{(3x + 4)(x – 2)} – \frac{7(3x + 4)}{(3x + 4)(x – 2)} \]Step 3: Combine and simplify
โ Working:
\[ \text{Numerator} = 21x – 7(3x + 4) \] \[ = 21x – 21x – 28 \] \[ = -28 \]So the fraction is:
\[ \frac{-28}{3x^2 – 2x – 8} \]โ (M1, A1)
๐ Final Answer:
\( k = -28 \)
Question 18 (4 marks)
Rationalise the denominator and simplify fully:
\[ \frac{3\sqrt{5} + \sqrt{3}}{\sqrt{5} – \sqrt{3}} \]
๐ Worked Solution
Step 1: Multiply by the conjugate
๐ก Strategy: To remove surds from the bottom, multiply the numerator and denominator by \( \sqrt{5} + \sqrt{3} \).
โ Working:
\[ \frac{3\sqrt{5} + \sqrt{3}}{\sqrt{5} – \sqrt{3}} \times \frac{\sqrt{5} + \sqrt{3}}{\sqrt{5} + \sqrt{3}} \]โ (M1)
Step 2: Expand the numerator and denominator
โ Working:
Denominator:
\[ (\sqrt{5} – \sqrt{3})(\sqrt{5} + \sqrt{3}) = 5 – 3 = 2 \]Numerator:
\[ (3\sqrt{5} + \sqrt{3})(\sqrt{5} + \sqrt{3}) \] \[ = 3(5) + 3\sqrt{15} + \sqrt{15} + 3 \] \[ = 15 + 4\sqrt{15} + 3 \] \[ = 18 + 4\sqrt{15} \]โ (M1, M1)
Step 3: Simplify the fraction
โ Working:
\[ \frac{18 + 4\sqrt{15}}{2} \] \[ = 9 + 2\sqrt{15} \]โ (A1)
๐ Final Answer:
\( 9 + 2\sqrt{15} \)
Question 19 (5 marks)
The equation of a curve is \( y = x^3 – 3x^2 + 5 \)
Work out the stationary points of the curve and determine their nature.
You must show your working.
๐ Worked Solution
Step 1: Differentiate and set to zero
๐ก Why we do this: Stationary points occur where the gradient (\( \frac{dy}{dx} \)) is zero.
โ Working:
\[ \frac{dy}{dx} = 3x^2 – 6x \]Set to 0:
\[ 3x^2 – 6x = 0 \] \[ 3x(x – 2) = 0 \]So, \( x = 0 \) or \( x = 2 \).
โ (M1, A1)
Step 2: Find y-coordinates
โ Working:
When \( x = 0 \):
\[ y = 0^3 – 3(0)^2 + 5 = 5 \implies (0, 5) \]When \( x = 2 \):
\[ y = 2^3 – 3(2)^2 + 5 \] \[ y = 8 – 12 + 5 = 1 \implies (2, 1) \]Step 3: Determine nature using the second derivative
๐ก How: We find \( \frac{d^2y}{dx^2} \). If it’s positive, it’s a minimum. If negative, it’s a maximum.
โ Working:
\[ \frac{d^2y}{dx^2} = 6x – 6 \]At \( x = 0 \):
\[ 6(0) – 6 = -6 \quad (< 0 \text{ Maximum}) \]At \( x = 2 \):
\[ 6(2) – 6 = 6 \quad (> 0 \text{ Minimum}) \]โ (M1, A1)
๐ Final Answer:
(0, 5) Maximum
(2, 1) Minimum
Question 20 (4 marks)
Here is the graph of \( y = -x^2 + 3x + 6 \) for \( -2 \le x \le 5 \)
By drawing a suitable straight line, work out approximate solutions to
\[ x^2 – \frac{7}{2}x – 3 = 0 \]
๐ Worked Solution
Step 1: Manipulate the equation to match the graph
๐ก Strategy: We have the graph of \( y = -x^2 + 3x + 6 \). We need to solve \( x^2 – 3.5x – 3 = 0 \).
Rearrange the target equation to look like the graph equation.
โ Working:
Target: \( x^2 – 3.5x – 3 = 0 \)
Multiply by -1: \( -x^2 + 3.5x + 3 = 0 \)
We want \( -x^2 + 3x + 6 \) on the LHS.
Add \( -0.5x \) and \( +3 \) to the equation to adjust coefficients:
\[ (-x^2 + 3.5x + 3) + (-0.5x + 3) = 0 + (-0.5x + 3) \] \[ -x^2 + 3x + 6 = -0.5x + 3 \]โ (B2 for identifying line)
Step 2: Identify the line to draw
๐ก Insight: The intersection of the curve \( y = -x^2 + 3x + 6 \) and the line \( y = -0.5x + 3 \) gives the solutions.
Draw line \( y = -0.5x + 3 \):
- When \( x = 0, y = 3 \)
- When \( x = 6, y = 0 \)
โ Working:
Draw the straight line passing through (0, 3) and (4, 1).
โ (M1 for drawing line)
Step 3: Read intersections
โ Working:
The line intersects the curve at approx \( x = -0.7 \) and \( x = 4.2 \).
โ (A1)
๐ Final Answer:
\( x \approx -0.7 \) and \( x \approx 4.2 \)
Question 21 (5 marks)
\( (2^{x+3})^{4x+1} = 8^{x-1} \)
Work out the possible values of \( x \).
๐ Worked Solution
Step 1: Express bases as powers of 2
๐ก Strategy: To solve exponential equations, get the same base on both sides. Note that \( 8 = 2^3 \).
โ Working:
\[ \text{LHS} = 2^{(x+3)(4x+1)} \] \[ \text{RHS} = (2^3)^{x-1} = 2^{3(x-1)} \]โ (M1)
Step 2: Equate powers and expand
โ Working:
\[ (x+3)(4x+1) = 3(x-1) \] \[ 4x^2 + x + 12x + 3 = 3x – 3 \] \[ 4x^2 + 13x + 3 = 3x – 3 \]โ (M1 for expansion)
Step 3: Solve the quadratic
โ Working:
\[ 4x^2 + 10x + 6 = 0 \]Divide by 2:
\[ 2x^2 + 5x + 3 = 0 \]Factorise:
\[ (2x + 3)(x + 1) = 0 \]Solutions:
\[ x = -1.5 \quad \text{or} \quad x = -1 \]โ (M1 for solving, A1 for answers)
๐ Final Answer:
\( x = -1.5 \) and \( x = -1 \)
Question 22 (4 marks)
\( f(x) = \frac{3 \sin x \cos x + \sin^2 x}{12 \cos^2 x + 4 \sin x \cos x} \)
Simplify \( f(x) \) and hence solve \( f(x) = -\frac{\sqrt{3}}{4} \) for \( 90^{\circ} < x < 180^{\circ} \)
You must show your working.
๐ Worked Solution
Step 1: Factorise numerator and denominator
๐ก Strategy: Look for common factors to simplify the fraction.
โ Working:
Numerator: \( \sin x (3 \cos x + \sin x) \)
Denominator: \( 4 \cos x (3 \cos x + \sin x) \)
โ (M1)
Step 2: Simplify to tan x
โ Working:
Cancel \( (3 \cos x + \sin x) \):
\[ f(x) = \frac{\sin x}{4 \cos x} = \frac{1}{4} \tan x \]โ (M1)
Step 3: Solve the equation
โ Working:
\[ \frac{1}{4} \tan x = -\frac{\sqrt{3}}{4} \] \[ \tan x = -\sqrt{3} \]The reference angle where \( \tan \alpha = \sqrt{3} \) is \( 60^{\circ} \).
Since \( \tan \) is negative in the 2nd quadrant (\( 90 < x < 180 \)):
\[ x = 180^{\circ} – 60^{\circ} = 120^{\circ} \]โ (A1)
๐ Final Answer:
\( 120^{\circ} \)
Question 23 (5 marks)
The \( n \)th term of a quadratic sequence is \( an^2 – 5n + c \) where \( a \) and \( c \) are integers.
The first four terms of the sequence are:
2 \( x \) 16 \( y \)
Work out the values of \( x \) and \( y \).
๐ Worked Solution
Step 1: Use given terms to find a and c
๐ก Strategy: We know the 1st term (n=1) is 2, and the 3rd term (n=3) is 16. We can create simultaneous equations.
โ Working:
For n=1 (Term = 2):
\[ a(1)^2 – 5(1) + c = 2 \] \[ a – 5 + c = 2 \implies a + c = 7 \quad \text{(1)} \]For n=3 (Term = 16):
\[ a(3)^2 – 5(3) + c = 16 \] \[ 9a – 15 + c = 16 \implies 9a + c = 31 \quad \text{(2)} \]โ (M1, M1)
Step 2: Solve for a and c
โ Working:
Subtract (1) from (2):
\[ 8a = 24 \implies a = 3 \]Substitute into (1):
\[ 3 + c = 7 \implies c = 4 \]The nth term rule is \( 3n^2 – 5n + 4 \).
โ (M1)
Step 3: Calculate x and y
โ Working:
Find x (n=2):
\[ x = 3(2)^2 – 5(2) + 4 \] \[ x = 12 – 10 + 4 = 6 \]Find y (n=4):
\[ y = 3(4)^2 – 5(4) + 4 \] \[ y = 48 – 20 + 4 = 32 \]โ (A1, A1)
๐ Final Answer:
\( x = 6, \quad y = 32 \)