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A-Level Maths H2 Quiz - Algebra Functions
Name: ____________________
Class: ____________________
Date: ____________________
Score: ________ / 65
Duration: 90 Minutes
Total Marks: 65
Instructions: Answer all questions. Show all necessary working. You may use an approved graphing calculator (non-CAS).
Section A: Functions and Composites (Questions 1–8)
Given f ( x ) = 2 x + 3 f(x) = 2x + 3 f ( x ) = 2 x + 3 and g ( x ) = x 2 − 1 g(x) = x^2 - 1 g ( x ) = x 2 − 1 , find the expression for f g ( x ) fg(x) f g ( x ) . [2]
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A-Level Maths H2 Quiz - Algebra Functions (Answer Key)
Section A: Functions and Composites
f g ( x ) = f ( x 2 − 1 ) = 2 ( x 2 − 1 ) + 3 = 2 x 2 − 2 + 3 = 2 x 2 + 1 fg(x) = f(x^2 - 1) = 2(x^2 - 1) + 3 = 2x^2 - 2 + 3 = 2x^2 + 1 f g ( x ) = f ( x 2 − 1 ) = 2 ( x 2 − 1 ) + 3 = 2 x 2 − 2 + 3 = 2 x 2 + 1 [2]
f ( x ) = x + 1 x − 2 f(x) = \frac{x+1}{x-2} f ( x ) = x − 2 x + 1 .
f − 1 ( x ) f^{-1}(x) f − 1 ( x ) : Let y = x + 1 x − 2 ⟹ y ( x − 2 ) = x + 1 ⟹ x y − 2 y = x + 1 ⟹ x ( y − 1 ) = 2 y + 1 ⟹ x = 2 y + 1 y − 1 y = \frac{x+1}{x-2} \implies y(x-2) = x+1 \implies xy - 2y = x+1 \implies x(y-1) = 2y+1 \implies x = \frac{2y+1}{y-1} y = x − 2 x + 1 ⟹ y ( x − 2 ) = x + 1 ⟹ x y − 2 y = x + 1 ⟹ x ( y − 1 ) = 2 y + 1 ⟹ x = y − 1 2 y + 1 .
Therefore, f − 1 ( x ) = 2 x + 1 x − 1 f^{-1}(x) = \frac{2x+1}{x-1} f − 1 ( x ) = x − 1 2 x + 1 . [3]
f ( x ) = x 2 − 4 x + 7 f(x) = x^2 - 4x + 7 f ( x ) = x 2 − 4 x + 7 .
Completing the square: f ( x ) = ( x − 2 ) 2 + 3 f(x) = (x-2)^2 + 3 f ( x ) = ( x − 2 ) 2 + 3 .
Domain: x ∈ R x \in \mathbb{R} x ∈ R .
Range: f ( x ) ≥ 3 f(x) \geq 3 f ( x ) ≥ 3 . [3]
f ( x ) = x − 3 f(x) = \sqrt{x-3} f ( x ) = x − 3 .
Domain: x − 3 ≥ 0 ⟹ x ≥ 3 x-3 \geq 0 \implies x \geq 3 x − 3 ≥ 0 ⟹ x ≥ 3 . [2]
f ( x ) = 1 x + 2 f(x) = \frac{1}{x+2} f ( x ) = x + 2 1 .
f ( f ( x ) ) = 1 1 x + 2 + 2 = 1 1 + 2 x + 4 x + 2 = x + 2 2 x + 5 f(f(x)) = \frac{1}{\frac{1}{x+2} + 2} = \frac{1}{\frac{1 + 2x + 4}{x+2}} = \frac{x+2}{2x+5} f ( f ( x )) = x + 2 1 + 2 1 = x + 2 1 + 2 x + 4 1 = 2 x + 5 x + 2 . [3]
f ( x ) = 3 x − 5 f(x) = 3x - 5 f ( x ) = 3 x − 5 .
f ( x ) = f − 1 ( x ) ⟹ 3 x − 5 = x + 5 3 ⟹ 9 x − 15 = x + 5 ⟹ 8 x = 20 ⟹ x = 2.5 f(x) = f^{-1}(x) \implies 3x - 5 = \frac{x+5}{3} \implies 9x - 15 = x + 5 \implies 8x = 20 \implies x = 2.5 f ( x ) = f − 1 ( x ) ⟹ 3 x − 5 = 3 x + 5 ⟹ 9 x − 15 = x + 5 ⟹ 8 x = 20 ⟹ x = 2.5 . [3]
f ( x ) = x 2 + 2 x − 3 f(x) = x^2 + 2x - 3 f ( x ) = x 2 + 2 x − 3 .
f ( x ) = 0 ⟹ ( x + 3 ) ( x − 1 ) = 0 ⟹ x = − 3 , 1 f(x) = 0 \implies (x+3)(x-1) = 0 \implies x = -3, 1 f ( x ) = 0 ⟹ ( x + 3 ) ( x − 1 ) = 0 ⟹ x = − 3 , 1 . [2]
f ( x ) = e 2 x f(x) = e^{2x} f ( x ) = e 2 x .
f − 1 ( x ) = 1 2 ln x f^{-1}(x) = \frac{1}{2} \ln x f − 1 ( x ) = 2 1 ln x . [2]
Section B: Modulus Functions and Inequalities
∣ 2 x − 5 ∣ < 3 ⟹ − 3 < 2 x − 5 < 3 ⟹ 2 < 2 x < 8 ⟹ 1 < x < 4 |2x - 5| < 3 \implies -3 < 2x - 5 < 3 \implies 2 < 2x < 8 \implies 1 < x < 4 ∣2 x − 5∣ < 3 ⟹ − 3 < 2 x − 5 < 3 ⟹ 2 < 2 x < 8 ⟹ 1 < x < 4 . [3]
∣ x + 2 ∣ ≥ 5 ⟹ x + 2 ≥ 5 |x + 2| \geq 5 \implies x + 2 \geq 5 ∣ x + 2∣ ≥ 5 ⟹ x + 2 ≥ 5 or x + 2 ≤ − 5 ⟹ x ≥ 3 x + 2 \leq -5 \implies x \geq 3 x + 2 ≤ − 5 ⟹ x ≥ 3 or x ≤ − 7 x \leq -7 x ≤ − 7 . [3]
f ( x ) = ∣ x − 3 ∣ + ∣ x + 1 ∣ f(x) = |x - 3| + |x + 1| f ( x ) = ∣ x − 3∣ + ∣ x + 1∣ .
For x < − 1 x < -1 x < − 1 : f ( x ) = − ( x − 3 ) − ( x + 1 ) = − 2 x + 2 f(x) = -(x-3) - (x+1) = -2x + 2 f ( x ) = − ( x − 3 ) − ( x + 1 ) = − 2 x + 2 .
For − 1 ≤ x < 3 -1 \leq x < 3 − 1 ≤ x < 3 : f ( x ) = − ( x − 3 ) + ( x + 1 ) = 4 f(x) = -(x-3) + (x+1) = 4 f ( x ) = − ( x − 3 ) + ( x + 1 ) = 4 .
For x ≥ 3 x \geq 3 x ≥ 3 : f ( x ) = ( x − 3 ) + ( x + 1 ) = 2 x − 2 f(x) = (x-3) + (x+1) = 2x - 2 f ( x ) = ( x − 3 ) + ( x + 1 ) = 2 x − 2 . [5]
∣ 3 x − 2 ∣ = ∣ x + 4 ∣ |3x - 2| = |x + 4| ∣3 x − 2∣ = ∣ x + 4∣ .
3 x − 2 = x + 4 ⟹ 2 x = 6 ⟹ x = 3 3x - 2 = x + 4 \implies 2x = 6 \implies x = 3 3 x − 2 = x + 4 ⟹ 2 x = 6 ⟹ x = 3 .
3 x − 2 = − ( x + 4 ) ⟹ 4 x = − 2 ⟹ x = − 0.5 3x - 2 = -(x + 4) \implies 4x = -2 \implies x = -0.5 3 x − 2 = − ( x + 4 ) ⟹ 4 x = − 2 ⟹ x = − 0.5 . [4]
f ( x ) = ∣ 2 x − 1 ∣ − 3 f(x) = |2x - 1| - 3 f ( x ) = ∣2 x − 1∣ − 3 .
Vertex: 2 x − 1 = 0 ⟹ x = 0.5 2x - 1 = 0 \implies x = 0.5 2 x − 1 = 0 ⟹ x = 0.5 . f ( 0.5 ) = − 3 f(0.5) = -3 f ( 0.5 ) = − 3 .
x-intercepts: ∣ 2 x − 1 ∣ = 3 ⟹ 2 x − 1 = 3 |2x - 1| = 3 \implies 2x - 1 = 3 ∣2 x − 1∣ = 3 ⟹ 2 x − 1 = 3 or 2 x − 1 = − 3 ⟹ x = 2 2x - 1 = -3 \implies x = 2 2 x − 1 = − 3 ⟹ x = 2 or x = − 1 x = -1 x = − 1 . [5]
∣ x − 1 ∣ + ∣ x − 4 ∣ = 3 |x - 1| + |x - 4| = 3 ∣ x − 1∣ + ∣ x − 4∣ = 3 .
x < 1 x < 1 x < 1 : − ( x − 1 ) − ( x − 4 ) = 3 ⟹ − 2 x + 5 = 3 ⟹ x = 1 -(x-1) - (x-4) = 3 \implies -2x + 5 = 3 \implies x = 1 − ( x − 1 ) − ( x − 4 ) = 3 ⟹ − 2 x + 5 = 3 ⟹ x = 1 (not in range).
1 ≤ x < 4 1 \leq x < 4 1 ≤ x < 4 : − ( x − 1 ) + ( x − 4 ) = 3 ⟹ − 3 = 3 -(x-1) + (x-4) = 3 \implies -3 = 3 − ( x − 1 ) + ( x − 4 ) = 3 ⟹ − 3 = 3 (no solution). Wait, check: ( x − 1 ) (x-1) ( x − 1 ) is positive, ( x − 4 ) (x-4) ( x − 4 ) is negative.
Correct: ( x − 1 ) − ( x − 4 ) = 3 ⟹ 3 = 3 (x-1) - (x-4) = 3 \implies 3 = 3 ( x − 1 ) − ( x − 4 ) = 3 ⟹ 3 = 3 . This is true for all x ∈ [ 1 , 4 ] x \in [1, 4] x ∈ [ 1 , 4 ] .
x ≥ 4 x \geq 4 x ≥ 4 : ( x − 1 ) + ( x − 4 ) = 3 ⟹ 2 x − 5 = 3 ⟹ x = 4 (x-1) + (x-4) = 3 \implies 2x - 5 = 3 \implies x = 4 ( x − 1 ) + ( x − 4 ) = 3 ⟹ 2 x − 5 = 3 ⟹ x = 4 .
Solution: 1 ≤ x ≤ 4 1 \leq x \leq 4 1 ≤ x ≤ 4 . [5]
∣ x 2 − 4 ∣ < 3 |x^2 - 4| < 3 ∣ x 2 − 4∣ < 3 .
− 3 < x 2 − 4 < 3 ⟹ 1 < x 2 < 7 -3 < x^2 - 4 < 3 \implies 1 < x^2 < 7 − 3 < x 2 − 4 < 3 ⟹ 1 < x 2 < 7 .
1 < x < 7 1 < x < \sqrt{7} 1 < x < 7 or − 7 < x < − 1 -\sqrt{7} < x < -1 − 7 < x < − 1 . [6]
Section C: Advanced Algebra and Polynomials
f ( x ) = x 3 − 6 x 2 + 11 x − 6 f(x) = x^3 - 6x^2 + 11x - 6 f ( x ) = x 3 − 6 x 2 + 11 x − 6 .
Possible roots: ± 1 , ± 2 , ± 3 , ± 6 \pm 1, \pm 2, \pm 3, \pm 6 ± 1 , ± 2 , ± 3 , ± 6 .
f ( 1 ) = 1 − 6 + 11 − 6 = 0 f(1) = 1 - 6 + 11 - 6 = 0 f ( 1 ) = 1 − 6 + 11 − 6 = 0 .
( x − 1 ) ( x 2 − 5 x + 6 ) = ( x − 1 ) ( x − 2 ) ( x − 3 ) (x-1)(x^2 - 5x + 6) = (x-1)(x-2)(x-3) ( x − 1 ) ( x 2 − 5 x + 6 ) = ( x − 1 ) ( x − 2 ) ( x − 3 ) .
Roots: x = 1 , 2 , 3 x = 1, 2, 3 x = 1 , 2 , 3 . [5]
f ( x ) = 2 x 3 + a x 2 + b x + 4 f(x) = 2x^3 + ax^2 + bx + 4 f ( x ) = 2 x 3 + a x 2 + b x + 4 .
f ( 1 ) = 0 ⟹ 2 + a + b + 4 = 0 ⟹ a + b = − 6 f(1) = 0 \implies 2 + a + b + 4 = 0 \implies a + b = -6 f ( 1 ) = 0 ⟹ 2 + a + b + 4 = 0 ⟹ a + b = − 6 .
f ( − 2 ) = 0 ⟹ − 16 + 4 a − 2 b + 4 = 0 ⟹ 4 a − 2 b = 12 ⟹ 2 a − b = 6 f(-2) = 0 \implies -16 + 4a - 2b + 4 = 0 \implies 4a - 2b = 12 \implies 2a - b = 6 f ( − 2 ) = 0 ⟹ − 16 + 4 a − 2 b + 4 = 0 ⟹ 4 a − 2 b = 12 ⟹ 2 a − b = 6 .
Adding: 3 a = 0 ⟹ a = 0 3a = 0 \implies a = 0 3 a = 0 ⟹ a = 0 .
b = − 6 b = -6 b = − 6 . [6]
P ( x ) = x 4 − 5 x 2 + 4 P(x) = x^4 - 5x^2 + 4 P ( x ) = x 4 − 5 x 2 + 4 .
( x 2 − 1 ) ( x 2 − 4 ) = ( x − 1 ) ( x + 1 ) ( x − 2 ) ( x + 2 ) (x^2 - 1)(x^2 - 4) = (x-1)(x+1)(x-2)(x+2) ( x 2 − 1 ) ( x 2 − 4 ) = ( x − 1 ) ( x + 1 ) ( x − 2 ) ( x + 2 ) . [4]
f ( x ) = x 3 − 3 x + 2 f(x) = x^3 - 3x + 2 f ( x ) = x 3 − 3 x + 2 .
f ′ ( x ) = 3 x 2 − 3 f'(x) = 3x^2 - 3 f ′ ( x ) = 3 x 2 − 3 .
3 x 2 − 3 = 0 ⟹ x = ± 1 3x^2 - 3 = 0 \implies x = \pm 1 3 x 2 − 3 = 0 ⟹ x = ± 1 .
f ( 1 ) = 1 − 3 + 2 = 0 f(1) = 1 - 3 + 2 = 0 f ( 1 ) = 1 − 3 + 2 = 0 (Local Min).
f ( − 1 ) = − 1 + 3 + 2 = 4 f(-1) = -1 + 3 + 2 = 4 f ( − 1 ) = − 1 + 3 + 2 = 4 (Local Max). [6]
f ( x ) = x 3 + p x + q f(x) = x^3 + px + q f ( x ) = x 3 + p x + q .
f ′ ( x ) = 3 x 2 + p f'(x) = 3x^2 + p f ′ ( x ) = 3 x 2 + p .
For 3 distinct real roots, f ′ ( x ) = 0 f'(x) = 0 f ′ ( x ) = 0 must have 2 distinct roots ⟹ p < 0 \implies p < 0 ⟹ p < 0 .
Local max f ( − − p / 3 ) f(-\sqrt{-p/3}) f ( − − p /3 ) and local min f ( − p / 3 ) f(\sqrt{-p/3}) f ( − p /3 ) must have opposite signs.
f ( − p / 3 ) ⋅ f ( − − p / 3 ) < 0 f(\sqrt{-p/3}) \cdot f(-\sqrt{-p/3}) < 0 f ( − p /3 ) ⋅ f ( − − p /3 ) < 0 . [8]