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Level 2 Certificate Further Mathematics Paper 2 (June 2023)

Exam Information

  • Level: Level 2 Certificate
  • Paper: Paper 2 (Calculator)
  • Total Marks: 80
  • Time Allowed: 1 hour 45 minutes
  • Calculator: Allowed (No symbolic algebra)

Question 1 (3 marks)

Solve \[\frac{8d-3}{5} = \frac{3d-7}{2}\]

Worked Solution

Step 1: Understanding the Equation

💡 What are we being asked to do?

We need to find the value of \(d\) that satisfies this algebraic equation. Since we have fractions on both sides, our first goal is to eliminate them to make the equation simpler.

Step 2: Eliminate the Fractions (Cross-Multiply)

👉 How do we remove the denominators?

We multiply the entire left side by 2 (the right denominator) and the entire right side by 5 (the left denominator).

✏ Working:

\[ 2(8d – 3) = 5(3d – 7) \]

✓ (M1) Correct removal of fractions

Step 3: Expand and Solve

👉 Expand the brackets:

\[ 16d – 6 = 15d – 35 \]

✓ (M1) Expanding brackets correctly

👉 Rearrange to find d:

Subtract \(15d\) from both sides and add 6 to both sides.

\[ 16d – 15d = -35 + 6 \] \[ d = -29 \]

Final Answer:

\( d = -29 \)

✓ Total: 3 marks

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Question 2 (4 marks)

(a) The first four terms of a linear sequence are:

15     18.5     22     25.5

Work out an expression for the \(n\)th term.

(b) A different linear sequence has \(n\)th term \(318 – 9n\).

Work out the value of the first negative term in the sequence.

Worked Solution

Part (a): Finding the nth term

💡 Strategy:

A linear sequence has the form \(dn + c\), where \(d\) is the common difference.

1. Find the difference:

\[ 18.5 – 15 = 3.5 \] \[ 22 – 18.5 = 3.5 \]

So the expression starts with \(3.5n\).

2. Find the constant term (Zeroth term):

Subtract the difference from the first term: \(15 – 3.5 = 11.5\).

Answer (a): \( 3.5n + 11.5 \)

Part (b): First negative term

💡 What condition makes a term negative?

We need the term to be less than zero: \( \text{term} < 0 \).

✏ Working:

\[ 318 – 9n < 0 \] \[ 318 < 9n \] \[ \frac{318}{9} < n \]

Using calculator:

\[ 35.333… < n \]

Since \(n\) must be a whole number (position in sequence), the first integer greater than 35.33 is \(n = 36\).

👉 Calculate the value of the 36th term:

\[ \text{Value} = 318 – 9(36) \] \[ = 318 – 324 \] \[ = -6 \]

✓ (B2) Correct value found

Final Answer:

(a) \( 3.5n + 11.5 \)
(b) \( -6 \)

✓ Total: 4 marks

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Question 3 (2 marks)

\[ \begin{pmatrix} 3 & 5 \\ u & 2 \end{pmatrix} \begin{pmatrix} 1 \\ 4 \end{pmatrix} = \begin{pmatrix} t \\ 6 \end{pmatrix} \]

Work out the values of \(t\) and \(u\).

Worked Solution

Step 1: Matrix Multiplication Rule

💡 How do we multiply matrices?

Multiply rows of the first matrix by columns of the second.

Top row calculation: \( (3 \times 1) + (5 \times 4) = t \)

Bottom row calculation: \( (u \times 1) + (2 \times 4) = 6 \)

Step 2: Solve for t
\[ t = 3 + 20 \] \[ t = 23 \]
Step 3: Solve for u
\[ u + 8 = 6 \] \[ u = 6 – 8 \] \[ u = -2 \]

Final Answer:

\( t = 23, \quad u = -2 \)

✓ Total: 2 marks

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Question 4 (4 marks)

A line passes through \(P(1, k)\) and \(Q(r, 6)\) where \(k\) and \(r\) are constants.

The midpoint of \(PQ\) has \(x\)-coordinate 5.

The gradient of the line is 2.

Work out the value of \(k\).

Worked Solution

Step 1: Use the Midpoint Information

💡 Formula: Midpoint \(x\) = \(\frac{x_1 + x_2}{2}\)

We know \(x_1 = 1\), \(x_2 = r\), and the midpoint is 5.

\[ \frac{1 + r}{2} = 5 \] \[ 1 + r = 10 \] \[ r = 9 \]

✓ (M1) Found value of r

Step 2: Use the Gradient Information

💡 Formula: Gradient \(m = \frac{y_2 – y_1}{x_2 – x_1}\)

We know points are \(P(1, k)\) and \(Q(9, 6)\), and gradient is 2.

\[ \frac{6 – k}{9 – 1} = 2 \] \[ \frac{6 – k}{8} = 2 \]

✓ (M1) Set up gradient equation

Step 3: Solve for k
\[ 6 – k = 2 \times 8 \] \[ 6 – k = 16 \] \[ -k = 10 \] \[ k = -10 \]

✓ (A1) Correct answer

Final Answer:

\( k = -10 \)

✓ Total: 4 marks

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Question 5 (3 marks)

\( y = 0.5x^4 \)

Work out the value of \(x\) for which the rate of change of \(y\) with respect to \(x\) is 6.75

Worked Solution

Step 1: Find the Rate of Change (Differentiation)

💡 Concept: “Rate of change of \(y\) with respect to \(x\)” means find the derivative \(\frac{dy}{dx}\).

Using power rule: Multiply by power, reduce power by 1.

\[ y = 0.5x^4 \] \[ \frac{dy}{dx} = 4 \times 0.5x^3 \] \[ \frac{dy}{dx} = 2x^3 \]

✓ (M1) Correct derivative

Step 2: Solve for x

We are told the rate of change is 6.75, so set the derivative equal to 6.75.

\[ 2x^3 = 6.75 \] \[ x^3 = \frac{6.75}{2} \] \[ x^3 = 3.375 \]

Take the cube root:

\[ x = \sqrt[3]{3.375} \] \[ x = 1.5 \]

Final Answer:

\( x = 1.5 \)

✓ Total: 3 marks

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Question 6 (2 marks)

The equation of a circle is \( (x + 7)^2 + (y – 4)^2 = 36 \)

Complete these statements.

The coordinates of the centre of the circle are ( ________ , ________ )

The radius of the circle is ________

Worked Solution

Step 1: Compare with Standard Form

💡 Formula: The standard equation of a circle is \( (x – a)^2 + (y – b)^2 = r^2 \), where \((a, b)\) is the centre and \(r\) is the radius.

Equation: \( (x + 7)^2 + (y – 4)^2 = 36 \)

Comparing \( (x – a)^2 \) with \( (x + 7)^2 \):

\[ -a = 7 \implies a = -7 \]

Comparing \( (y – b)^2 \) with \( (y – 4)^2 \):

\[ -b = -4 \implies b = 4 \]

Comparing \( r^2 \) with \( 36 \):

\[ r = \sqrt{36} = 6 \]

Final Answer:

Centre: \( (-7, 4) \)

Radius: \( 6 \)

✓ Total: 2 marks

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Question 7 (3 marks)

Here is a sketch of the curve \( y = ax^2 + bx + c \) where \(a\), \(b\) and \(c\) are constants.

The curve intersects the \(x\)-axis at \((-4, 0)\) and \((p, 0)\).

The turning point has \(x\)-coordinate 0.5.

x y O -4 p 0.5

(a) Work out the value of \(p\).

(b) Solve \( ax^2 + bx + c > 0 \)

Worked Solution

Part (a): Find p

💡 Property of Quadratics: A quadratic curve is symmetrical. The turning point lies exactly halfway between the two roots (x-intercepts).

Roots are at \(x = -4\) and \(x = p\). The midpoint is \(x = 0.5\).

Midpoint formula:

\[ \frac{-4 + p}{2} = 0.5 \] \[ -4 + p = 0.5 \times 2 \] \[ -4 + p = 1 \] \[ p = 5 \]

✓ (B1) Correct value

Part (b): Solve the inequality

💡 What does \( > 0 \) mean?

\( ax^2 + bx + c \) represents the \(y\)-value of the curve. We need to find the \(x\) values where the curve is above the x-axis (\(y > 0\)).

From the sketch, the curve is above the axis to the left of -4 and to the right of \(p\) (which is 5).

So, \(x\) must be less than -4 OR greater than 5.

\[ x < -4 \quad \text{or} \quad x > 5 \]

Final Answer:

(a) \( p = 5 \)

(b) \( x < -4 \) or \( x > 5 \)

✓ Total: 3 marks

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Question 8 (4 marks)

\(ABC\) is a triangle with perpendicular height \(AD\).

Area of \(ABC = 25 \text{ cm}^2\)

\(BD : DC = 2 : 3\)

Work out the size of angle \(w\).

A B C D 4 cm w

Worked Solution

Step 1: Calculate the length of the base BC

💡 Formula: Area of triangle = \(\frac{1}{2} \times \text{base} \times \text{height}\)

We know Area = 25 and Height (\(AD\)) = 4.

\[ 25 = \frac{1}{2} \times BC \times 4 \] \[ 25 = 2 \times BC \] \[ BC = 12.5 \text{ cm} \]

✓ (M1) Correct base calculation

Step 2: Calculate length DC using Ratio

The base \(BC\) is split into parts \(BD\) and \(DC\) in the ratio \(2:3\).

Total parts = \(2 + 3 = 5\).

We need length \(DC\) (which corresponds to the 3 parts) to use in the right-angled triangle \(ADC\).

Length of 1 part = \(12.5 \div 5 = 2.5 \text{ cm}\)

Length \(DC = 3 \times 2.5 = 7.5 \text{ cm}\)

✓ (M1) Correct length DC

Step 3: Calculate angle w using Trigonometry

In right-angled triangle \(ADC\):

  • Opposite (\(AD\)) = 4
  • Adjacent (\(DC\)) = 7.5
  • We need angle \(w\) (at \(C\)).

💡 SOH CAH TOA: We have Opposite and Adjacent, so use Tan.

\[ \tan(w) = \frac{\text{Opp}}{\text{Adj}} \] \[ \tan(w) = \frac{4}{7.5} \] \[ w = \tan^{-1}\left(\frac{4}{7.5}\right) \] \[ w = 28.072… \]

Final Answer:

\( w = 28.1^\circ \) (to 1 d.p.)

✓ Total: 4 marks

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Question 9 (7 marks total)

The dimensions of a cuboid are given in centimetres.

3x 2x x + 2y

The total length of all 12 edges is 300 cm.

(a) Show that \( y = \frac{75 – 6x}{2} \)

(b) The volume of the cuboid is \(V\) cm\(^3\). Show that \( V = 450x^2 – 30x^3 \)

(c) Use calculus to work out the maximum value of \(V\) as \(x\) varies.

Worked Solution

Part (a): Edge Length Equation

A cuboid has 12 edges: 4 lengths, 4 widths, and 4 heights.

Dimensions are \(3x\), \(2x\), and \((x + 2y)\).

Total length = \(4(3x) + 4(2x) + 4(x + 2y) = 300\)

Divide by 4 to simplify:

\[ 3x + 2x + (x + 2y) = 75 \] \[ 6x + 2y = 75 \]

Rearrange for \(y\):

\[ 2y = 75 – 6x \] \[ y = \frac{75 – 6x}{2} \]

✓ (A1) Shown

Part (b): Volume Equation

💡 Formula: Volume = Length × Width × Height

\[ V = 3x \times 2x \times (x + 2y) \] \[ V = 6x^2(x + 2y) \]

Substitute \(2y = 75 – 6x\) from part (a):

\[ V = 6x^2(x + (75 – 6x)/2 \times 2 / 2) \]

Wait, easier substitution: Note that \(x + 2y\) is the height. Let’s substitute \(y\).

\[ V = 3x \times 2x \times (x + 2(\frac{75-6x}{2})) \] \[ V = 6x^2 (x + 75 – 6x) \] \[ V = 6x^2 (75 – 5x) \] \[ V = 450x^2 – 30x^3 \]

✓ (A1) Shown

Part (c): Maximize Volume

💡 Strategy: To find a maximum using calculus, differentiate \(V\) with respect to \(x\) (\(\frac{dV}{dx}\)), set it to 0, and solve.

1. Differentiate:

\[ V = 450x^2 – 30x^3 \] \[ \frac{dV}{dx} = 2 \times 450x – 3 \times 30x^2 \] \[ \frac{dV}{dx} = 900x – 90x^2 \]

2. Set to 0:

\[ 900x – 90x^2 = 0 \]

Factorise:

\[ 90x(10 – x) = 0 \]

So \(x = 0\) or \(x = 10\).

Since \(x\) is a length, \(x \neq 0\), so \(x = 10\).

3. Calculate Max Volume:

Substitute \(x = 10\) back into \(V\):

\[ V = 450(10)^2 – 30(10)^3 \] \[ V = 450(100) – 30(1000) \] \[ V = 45000 – 30000 \] \[ V = 15000 \]

Final Answer:

Max Volume = 15000 cm\(^3\)

✓ Total: 7 marks

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Question 10 (3 marks)

Line \(K\) has equation \(4x – 5y = 17\)

Line \(L\) passes through the points \((3, 6)\) and \((-5, 16)\)

Tick (✓) the correct statement about lines \(K\) and \(L\).

The lines are parallel.
The lines are perpendicular.
The lines are neither parallel nor perpendicular.

Show working to support your answer.

Worked Solution

Step 1: Find Gradient of Line K

Rearrange \(4x – 5y = 17\) into the form \(y = mx + c\) to read the gradient \(m\).

\[ 4x – 17 = 5y \] \[ y = \frac{4}{5}x – \frac{17}{5} \]

Gradient \(m_K = \frac{4}{5}\) or 0.8

✓ (M1) Gradient of K found

Step 2: Find Gradient of Line L

Use formula \(m = \frac{y_2 – y_1}{x_2 – x_1}\) with points \((3, 6)\) and \((-5, 16)\).

\[ m_L = \frac{16 – 6}{-5 – 3} \] \[ m_L = \frac{10}{-8} \] \[ m_L = -\frac{5}{4} \text{ or } -1.25 \]

✓ (M1) Gradient of L found

Step 3: Compare Gradients

Rules:

  • Parallel if gradients are equal.
  • Perpendicular if product of gradients is -1 (\(m_1 \times m_2 = -1\)).
\[ m_K \times m_L = \frac{4}{5} \times -\frac{5}{4} = -1 \]

Since the product is -1, they are perpendicular.

Final Answer:

✓ The lines are perpendicular.

✓ Total: 3 marks

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Question 11 (4 marks)

Expand and simplify fully \[(2x^3 – 9)(3x^2 + 4) + x(x – 4)^2\]

Worked Solution

Step 1: Expand the double brackets

💡 Strategy: Use FOIL (First, Outer, Inner, Last) for the first part.

\((2x^3 – 9)(3x^2 + 4)\)

\[ 2x^3 \times 3x^2 = 6x^5 \] \[ 2x^3 \times 4 = 8x^3 \] \[ -9 \times 3x^2 = -27x^2 \] \[ -9 \times 4 = -36 \]

Result 1: \( 6x^5 + 8x^3 – 27x^2 – 36 \)

✓ (M1) First expansion correct

Step 2: Expand the second part

First expand \((x – 4)^2\), then multiply by \(x\).

\[ (x – 4)^2 = (x – 4)(x – 4) = x^2 – 8x + 16 \]

Now multiply by \(x\):

\[ x(x^2 – 8x + 16) = x^3 – 8x^2 + 16x \]

✓ (M1) Second expansion correct

Step 3: Collect like terms

Add the two results together:

\( (6x^5 + 8x^3 – 27x^2 – 36) + (x^3 – 8x^2 + 16x) \)

\(x^5\) terms: \(6x^5\)

\(x^3\) terms: \(8x^3 + x^3 = 9x^3\)

\(x^2\) terms: \(-27x^2 – 8x^2 = -35x^2\)

\(x\) terms: \(+16x\)

Constants: \(-36\)

\[ 6x^5 + 9x^3 – 35x^2 + 16x – 36 \]

✓ (A1) Fully simplified expression

Final Answer:

\( 6x^5 + 9x^3 – 35x^2 + 16x – 36 \)

✓ Total: 4 marks

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Question 12 (3 marks)

\(VABCD\) is a pyramid.

The square horizontal base, \(ABCD\), has side length 15 cm.

\(V\) is directly above the centre, \(X\), of the base.

\(VA = 28\) cm

V A B C D X 28 cm 15 cm

Work out the size of the angle that \(VA\) makes with \(ABCD\).

Worked Solution

Step 1: Identify the Angle

💡 3D Trigonometry Rule: The angle a line makes with a plane is the angle between the line (\(VA\)) and its projection on the plane (\(AX\)).

We need to find angle \( \angle VAX \).

Step 2: Calculate length AX

\(ABCD\) is a square with side 15 cm. \(AC\) is the diagonal.

\(X\) is the midpoint of \(AC\).

Diagonal AC (Pythagoras):

\[ AC^2 = 15^2 + 15^2 \] \[ AC = \sqrt{225 + 225} = \sqrt{450} \] \[ AC = 15\sqrt{2} \approx 21.213 \]

Length AX:

\[ AX = \frac{1}{2} AC = \frac{15\sqrt{2}}{2} \approx 10.6066 \text{ cm} \]

✓ (M1) Correct calculation of AX

Step 3: Calculate the Angle

In triangle \(VAX\):

  • \( \angle VXA = 90^\circ \) (V is directly above X)
  • Hypotenuse \( VA = 28 \)
  • Adjacent \( AX = 10.6066… \)

Use Cosine: \( \cos(\theta) = \frac{\text{Adj}}{\text{Hyp}} \)

\[ \cos(\theta) = \frac{10.6066}{28} \] \[ \theta = \cos^{-1}\left(\frac{10.6066}{28}\right) \] \[ \theta = 67.738… \]

✓ (M1) Correct trigonometry setup

Final Answer:

\( 67.7^\circ \) (to 1 d.p.)

✓ Total: 3 marks

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Question 13 (6 marks total)

(a) Circle the expression equivalent to \( 3x^{-7} \)

\( \frac{3}{x^7} \)
\( -\frac{1}{3x^7} \)
\( \frac{1}{3x^7} \)
\( \frac{3}{x^{-7}} \)

(b) Simplify fully \[\left(\frac{12w^8}{4w^3}\right)^2\]

(c) \( \sqrt{y} \times \sqrt[3]{y} = \sqrt[d]{y^c} \) where \(c\) and \(d\) are positive integers.

Work out the least possible values of \(c\) and \(d\).

Worked Solution

Part (a): Negative Indices

💡 Rule: \( x^{-n} = \frac{1}{x^n} \)

Only the \(x\) is raised to the power -7, not the 3.

\( 3x^{-7} = 3 \times \frac{1}{x^7} = \frac{3}{x^7} \)

Answer (a): \( \frac{3}{x^7} \) (First option)

Part (b): Simplify Fraction with Powers

Step 1: Simplify inside the bracket first.

\[ \frac{12w^8}{4w^3} \]

Numbers: \( 12 \div 4 = 3 \)

Powers (subtract): \( w^8 \div w^3 = w^{8-3} = w^5 \)

Inside expression: \( 3w^5 \)

Step 2: Square the result.

\[ (3w^5)^2 = 3^2 \times (w^5)^2 \] \[ = 9 \times w^{5 \times 2} \] \[ = 9w^{10} \]

✓ (B2) Fully simplified

Part (c): Roots to Fractional Powers

💡 Rule: \( \sqrt[n]{x} = x^{\frac{1}{n}} \)

\[ \sqrt{y} = y^{\frac{1}{2}} \] \[ \sqrt[3]{y} = y^{\frac{1}{3}} \]

Multiply them (add indices):

\[ y^{\frac{1}{2}} \times y^{\frac{1}{3}} = y^{\frac{1}{2} + \frac{1}{3}} \]

Add fractions:

\[ \frac{1}{2} + \frac{1}{3} = \frac{3}{6} + \frac{2}{6} = \frac{5}{6} \]

So the expression is \( y^{\frac{5}{6}} \)

Convert back to root form \( \sqrt[d]{y^c} = y^{\frac{c}{d}} \):

\[ y^{\frac{5}{6}} = \sqrt[6]{y^5} \]

Answer (c): \( c = 5, \quad d = 6 \)

Final Answers:

(a) \( \frac{3}{x^7} \)

(b) \( 9w^{10} \)

(c) \( c = 5, d = 6 \)

✓ Total: 6 marks

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Question 14 (4 marks)

Simplify fully \[ \frac{15a^2}{a^2 + 6a – 16} \times \frac{8 – 4a}{3a} \]

Worked Solution

Step 1: Factorise everything

💡 Strategy: Never multiply out first! Always factorise and cancel common terms.

1. Quadratic: \( a^2 + 6a – 16 \)

Factors of -16 that add to +6: \(+8\) and \(-2\).

\[ (a + 8)(a – 2) \]

2. Linear: \( 8 – 4a \)

Factor out 4:

\[ 4(2 – a) \]

Tip: Notice \( (2-a) \) is \( -(a-2) \). This helps with cancelling.

\[ -4(a – 2) \]
Step 2: Rewrite the expression
\[ \frac{15a^2}{(a+8)(a-2)} \times \frac{-4(a-2)}{3a} \]

✓ (M2) Correct factorisation

Step 3: Cancel common terms

Cancel \( (a-2) \):

\[ \frac{15a^2}{(a+8)} \times \frac{-4}{3a} \]

Cancel \( a \) from top and bottom:

\[ \frac{15a}{(a+8)} \times \frac{-4}{3} \]

Cancel \( 3 \) from 15 and 3:

\[ \frac{5a}{(a+8)} \times -4 \]
Step 4: Combine remaining terms
\[ \frac{5a \times -4}{a+8} = \frac{-20a}{a+8} \]

Or: \( -\frac{20a}{a+8} \)

✓ (A1) Fully simplified

Final Answer:

\( \frac{-20a}{a+8} \)

✓ Total: 4 marks

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Question 15 (4 marks)

The function \(g\) is given by \( g(x) = a \times b^x \) where \(a\) and \(b\) are constants.

The domain of the function is \( -1 \leqslant x \leqslant 2 \)

\( P\left(0, \frac{1}{2}\right) \) and \( Q\left(1, \frac{3}{2}\right) \) are points on the graph \( y = g(x) \)

x y O P Q -1 1 2 y = g(x)

Work out the range of the function.

Worked Solution

Step 1: Find constants a and b

Use the coordinates of \(P\) and \(Q\) in the equation \( g(x) = a \times b^x \).

Point P(0, 1/2):

\[ \frac{1}{2} = a \times b^0 \]

Since \( b^0 = 1 \):

\[ a = \frac{1}{2} \]

Point Q(1, 3/2):

\[ \frac{3}{2} = a \times b^1 \] \[ \frac{3}{2} = \frac{1}{2} \times b \] \[ b = 3 \]

So the function is \( g(x) = 0.5 \times 3^x \)

✓ (M1) Function found

Step 2: Calculate Range Values

The range is the set of possible \(y\) values.

Since the function is increasing (exponential with base > 1), the minimum y-value occurs at the minimum x-value, and maximum at maximum.

Domain: \( -1 \leqslant x \leqslant 2 \)

Minimum (at \(x = -1\)):

\[ g(-1) = 0.5 \times 3^{-1} \] \[ = \frac{1}{2} \times \frac{1}{3} = \frac{1}{6} \]

Maximum (at \(x = 2\)):

\[ g(2) = 0.5 \times 3^2 \] \[ = 0.5 \times 9 = 4.5 \text{ (or } \frac{9}{2}) \]

Final Answer:

\( \frac{1}{6} \leqslant g(x) \leqslant 4.5 \)

✓ Total: 4 marks

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Question 16 (4 marks)

\( (2x – 3) \) is a factor of \( 6x^3 – 25x^2 + 28x – 6 \)

Solve \( 6x^3 – 25x^2 + 28x – 6 = 0 \)

Give all solutions as exact values.

Worked Solution

Step 1: Perform Algebraic Division

💡 Strategy: Since \( (2x-3) \) is a factor, we can divide the cubic expression by \( (2x-3) \) to find the remaining quadratic factor.

We need to find \( (ax^2 + bx + c) \) such that:

\[ (2x – 3)(ax^2 + bx + c) = 6x^3 – 25x^2 + 28x – 6 \]

Compare coefficients:

1. \( x^3 \) term: \( 2x \times ax^2 = 6x^3 \Rightarrow 2a = 6 \Rightarrow a = 3 \)

2. Constant term: \( -3 \times c = -6 \Rightarrow c = 2 \)

3. \( x^2 \) term: \( 2x \times bx + (-3) \times ax^2 = -25x^2 \)

\[ 2b – 3(3) = -25 \] \[ 2b – 9 = -25 \] \[ 2b = -16 \Rightarrow b = -8 \]

So the quadratic factor is \( 3x^2 – 8x + 2 \).

✓ (M1) Quadratic factor found

Step 2: Solve the Linear Factor
\[ 2x – 3 = 0 \] \[ 2x = 3 \] \[ x = \frac{3}{2} \]
Step 3: Solve the Quadratic Factor

Solve \( 3x^2 – 8x + 2 = 0 \).

Since we need exact values and it doesn’t factorise easily, use the Quadratic Formula.

\[ x = \frac{-b \pm \sqrt{b^2 – 4ac}}{2a} \] \[ x = \frac{8 \pm \sqrt{(-8)^2 – 4(3)(2)}}{2(3)} \] \[ x = \frac{8 \pm \sqrt{64 – 24}}{6} \] \[ x = \frac{8 \pm \sqrt{40}}{6} \]

Simplify the surd \( \sqrt{40} = \sqrt{4 \times 10} = 2\sqrt{10} \):

\[ x = \frac{8 \pm 2\sqrt{10}}{6} \]

Divide top and bottom by 2:

\[ x = \frac{4 \pm \sqrt{10}}{3} \]

✓ (M1) Method for solving quadratic

Final Answer:

\( x = \frac{3}{2}, \quad x = \frac{4 + \sqrt{10}}{3}, \quad x = \frac{4 – \sqrt{10}}{3} \)

✓ Total: 4 marks

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Question 17 (4 marks)

The function \( h \) is given by \( h(x) = ax(3x^2 – 2) + 5x \) where \( a \) is a positive constant.

\( h \) is an increasing function for all values of \( x \).

Work out the possible values of \( a \).

Give your answer as an inequality.

Worked Solution

Step 1: Expand and Differentiate

💡 Concept: A function is increasing if its gradient (derivative) is greater than or equal to 0 for all \(x\).

First, expand \( h(x) \).

\[ h(x) = 3ax^3 – 2ax + 5x \]

Differentiate with respect to \( x \):

\[ h'(x) = 9ax^2 – 2a + 5 \]

✓ (M1) Correct derivative

Step 2: Set condition for increasing function

We need \( h'(x) \geqslant 0 \) for all values of \( x \).

The expression \( 9ax^2 – 2a + 5 \) is a quadratic in \( x \). Since \( a > 0 \), the coefficient of \( x^2 \) (\(9a\)) is positive, so it’s a “U-shaped” parabola.

For a U-shaped parabola to be always non-negative (\(\geqslant 0\)), its minimum point must be \(\geqslant 0\).

The minimum of \( y = px^2 + q \) occurs at \( x = 0 \).

Substitute \( x = 0 \) into \( h'(x) \):

\[ \text{Min value} = 9a(0)^2 – 2a + 5 = -2a + 5 \]

We require this minimum to be \(\geqslant 0\):

\[ -2a + 5 \geqslant 0 \]

✓ (M1) Setting up inequality

Step 3: Solve the inequality
\[ 5 \geqslant 2a \] \[ 2.5 \geqslant a \quad \text{or} \quad a \leqslant 2.5 \]

We are also told \( a \) is a positive constant.

So \( a > 0 \).

Final Answer:

\( 0 < a \leqslant 2.5 \)

✓ Total: 4 marks

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Question 18 (3 marks total)

Here is a sketch of \( y = \cos x \) for values of \( x \) from \( 0^\circ \) to \( 360^\circ \)

\( \alpha \) is an obtuse angle measured in degrees.

\( \cos \alpha = -k \) where \( k \) is a positive constant.

x y O 360° 90° 180° 270° 1 -1 -k α

(a) Tick (✓) two boxes that show expressions for \( x \) where \( \cos x = -k \)

(b) Circle the expression for \( x \) where \( \sin x = -k \)

\( \alpha \)
\( 90^\circ + \alpha \)
\( 180^\circ – \alpha \)
\( 180^\circ + \alpha \)

Worked Solution

Part (a): Solving cos(x) = -k

The graph of \( \cos x \) has symmetry.

The problem gives one solution as \( \alpha \). Looking at the graph, \( \cos x = -k \) intersects the curve at \( \alpha \) and another point.

The cosine graph is symmetrical about \( 360^\circ \) (and \( 0^\circ \)).

The solutions in the range \( 0^\circ \) to \( 360^\circ \) are \( \alpha \) and \( 360^\circ – \alpha \).

Also, the graph repeats every \( 360^\circ \). So \( 360^\circ + \alpha \) is also a solution.

Correct ticks:

✓ \( 360^\circ – \alpha \)

✓ \( 360^\circ + \alpha \)

Part (b): Solving sin(x) = -k

We know \( \cos \alpha = -k \).

We want to find \( x \) such that \( \sin x = -k \).

💡 Identity: \( \sin(90^\circ + \theta) = \cos \theta \).

Let’s check the options:

  • If \( x = 90^\circ + \alpha \):
  • \( \sin(90^\circ + \alpha) = \cos \alpha \)
  • Since \( \cos \alpha = -k \), then \( \sin(90^\circ + \alpha) = -k \).

Therefore, \( 90^\circ + \alpha \) is the correct expression.

Answer: \( 90^\circ + \alpha \)

Final Answers:

(a) \( 360^\circ – \alpha \) and \( 360^\circ + \alpha \)

(b) \( 90^\circ + \alpha \)

✓ Total: 3 marks

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Question 19 (3 marks)

In these simultaneous equations, \( k \) is a positive constant.

\[ 3x + 4y = k \] \[ y = 2kx \]

Solve the simultaneous equations.

Give the answers in their simplest form in terms of \( k \).

Worked Solution

Step 1: Substitute

💡 Strategy: Substitute the expression for \( y \) from the second equation into the first.

\[ 3x + 4(2kx) = k \] \[ 3x + 8kx = k \]

✓ (M1) Correct substitution

Step 2: Solve for x

Factorise \( x \) out on the left hand side.

\[ x(3 + 8k) = k \] \[ x = \frac{k}{3 + 8k} \]

✓ (A1) Correct x value

Step 3: Solve for y

Substitute \( x \) back into \( y = 2kx \).

\[ y = 2k \left( \frac{k}{3 + 8k} \right) \] \[ y = \frac{2k^2}{3 + 8k} \]

Final Answer:

\( x = \frac{k}{3+8k} \)

\( y = \frac{2k^2}{3+8k} \)

✓ Total: 3 marks

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Question 20 (3 marks)

Show that

\[ 2\sin^3 x + 2\sin x \cos^2 x + 5\tan x \cos x \]

simplifies to \( p\sin x \) where \( p \) is a constant.

Worked Solution

Step 1: Simplify the first two terms

Look for a common factor in \( 2\sin^3 x + 2\sin x \cos^2 x \).

We can factor out \( 2\sin x \).

\[ 2\sin x(\sin^2 x + \cos^2 x) \]

💡 Identity: \( \sin^2 x + \cos^2 x = 1 \)

\[ 2\sin x(1) = 2\sin x \]

✓ (M1) Used identity correctly

Step 2: Simplify the third term

Consider \( 5\tan x \cos x \).

💡 Identity: \( \tan x = \frac{\sin x}{\cos x} \)

\[ 5\left( \frac{\sin x}{\cos x} \right) \cos x \]

The \( \cos x \) terms cancel out:

\[ 5\sin x \]

✓ (M1) Simplified tan term

Step 3: Combine all terms
\[ 2\sin x + 5\sin x = 7\sin x \]

This is in the form \( p\sin x \) where \( p = 7 \).

✓ (A1) Correct final form

Final Answer:

\( 7\sin x \)

✓ Total: 3 marks

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Question 21 (4 marks)

\(A\), \(B\), \(C\), \(D\) and \(E\) are points on a circle, centre \(O\).

O A B D C E 2x 6x 7x

Work out the value of \( x \).

Worked Solution

Step 1: Use Circle Theorems for Center Angles

💡 Theorem: The angle at the centre is double the angle at the circumference.

Consider the angle \( \angle BCD = 6x \). This subtends the major arc \( BAD \). The corresponding angle at the centre is the reflex angle \( \angle BOD \).

\[ \text{Reflex } \angle BOD = 2 \times 6x = 12x \]

Consider the angle \( \angle AED = 7x \). This subtends the major arc \( ABD \). The corresponding angle at the centre is the reflex angle \( \angle AOD \).

\[ \text{Reflex } \angle AOD = 2 \times 7x = 14x \]
Step 2: Find Angle AOB

Consider triangle \( OAB \). Since \( OA \) and \( OB \) are radii, the triangle is isosceles.

We are given \( \angle OAB = 2x \). Therefore, \( \angle OBA = 2x \).

The angles in a triangle sum to \( 180^\circ \).

\[ \angle AOB = 180 – (2x + 2x) = 180 – 4x \]
Step 3: Form an Equation using Angles around the Center

The sum of the arcs \( AB \), \( BD \) (minor), and \( DA \) (minor) makes the full circle (\( 360^\circ \)).

Let’s convert our reflex angles into the minor angles at the centre:

  • Minor \( \angle BOD = 360 – 12x \)
  • Minor \( \angle AOD = 360 – 14x \)

The sum of these three minor angles (\( \angle AOB, \angle BOD, \angle AOD \)) is \( 360^\circ \).

\[ \angle AOB + \text{Minor } \angle BOD + \text{Minor } \angle AOD = 360 \] \[ (180 – 4x) + (360 – 12x) + (360 – 14x) = 360 \]

Simplify:

\[ 900 – 30x = 360 \] \[ 900 – 360 = 30x \] \[ 540 = 30x \] \[ x = \frac{540}{30} \] \[ x = 18 \]

✓ (A1) Correct value

Final Answer:

\( x = 18 \)

✓ Total: 4 marks

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Question 22 (3 marks)

Five-digit integers are made using

1   2   7   8   9

For each integer, all the digits are used exactly once.

The integers are:

  • greater than 40 000 and
  • odd.

How many different integers can be made?

You must show your working.

Worked Solution

Step 1: Identify Restrictions

Digits available: \( \{1, 2, 7, 8, 9\} \)

Condition 1 (> 40,000): The first digit must be 7, 8, or 9. (1 and 2 are too small).

Condition 2 (Odd): The last digit must be 1, 7, or 9. (2 and 8 are even).

We need to consider cases based on the first digit.

Step 2: Analyse Case 1 (Start with 7)

First digit: 7 (1 choice)

Last digit: Must be odd. Remaining odds are 1, 9. (2 choices)

Middle 3 digits: Arrange remaining 3 digits. (\(3! = 6\) choices)

Total for Case 1: \( 1 \times 2 \times 6 = 12 \)

Step 3: Analyse Case 2 (Start with 8)

First digit: 8 (1 choice)

Last digit: Must be odd. Odds are 1, 7, 9. (3 choices)

Middle 3 digits: Arrange remaining 3 digits. (\(3! = 6\) choices)

Total for Case 2: \( 1 \times 3 \times 6 = 18 \)

Step 4: Analyse Case 3 (Start with 9)

First digit: 9 (1 choice)

Last digit: Must be odd. Remaining odds are 1, 7. (2 choices)

Middle 3 digits: Arrange remaining 3 digits. (\(3! = 6\) choices)

Total for Case 3: \( 1 \times 2 \times 6 = 12 \)

Step 5: Total Calculation
\[ 12 + 18 + 12 = 42 \]

✓ (B3) Correct total

Final Answer:

42

✓ Total: 3 marks

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