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O Level Elementary Mathematics Algebra Functions Quiz

Free O Level E Maths Algebra Functions quiz, HY3 AI version, with questions, answers, and O Level-style practice for Singapore students.

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O Level Elementary Mathematics AI Generated Generated by Tencent HY3 Free Updated 2026-08-17

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Answers

O-Level Elementary Mathematics Quiz - Algebra Functions (Answer Key)

Topic: Algebra Functions
Total Marks: 40
Level: O-Level Elementary Mathematics


Section A: Basic Function Notation and Evaluation

1. [2 marks]
Given f(x)=3x4f(x) = 3x - 4, find f(5)f(5).

  • Substitute x=5x = 5: f(5)=3(5)4=154=11f(5) = 3(5) - 4 = 15 - 4 = 11.
    Answer: 11
    Teaching note: A function f(x)f(x) means "replace x with the given number". Common mistake: forgetting to multiply before subtracting.

2. [2 marks]
Given g(x)=x2+2xg(x) = x^2 + 2x, find g(3)g(-3).

  • g(3)=(3)2+2(3)=96=3g(-3) = (-3)^2 + 2(-3) = 9 - 6 = 3.
    Answer: 3
    Teaching note: (3)2=9(-3)^2 = 9, not 9-9. Squaring a negative gives positive.

3. [2 marks]
h(x)=10xh(x) = \frac{10}{x}, find h(2)h(2).

  • h(2)=102=5h(2) = \frac{10}{2} = 5.
    Answer: 5

4. [2 marks]
p(x)=5xp(x) = 5 - x, find xx when p(x)=0p(x) = 0.

  • 5x=0x=55 - x = 0 \Rightarrow x = 5.
    Answer: 5
    Marking: 1 mark for equation, 1 mark for solution.

5. [2 marks]
f(x)=2x+1f(x) = 2x + 1, find f(a+1)f(a+1).

  • f(a+1)=2(a+1)+1=2a+2+1=2a+3f(a+1) = 2(a+1) + 1 = 2a + 2 + 1 = 2a + 3.
    Answer: 2a+32a + 3
    Teaching note: Replace every x with (a+1)(a+1) inside brackets.

Section B: Graphs of Linear and Quadratic Functions

6. [2 marks]
y=2x+3y = 2x + 3: gradient = 2, y-intercept = 3.
Answer: Gradient 2, y-intercept 3
Teaching note: For y=mx+cy = mx + c, mm is gradient, cc is y-intercept.

7. [2 marks]
Sketch y=4xy = 4 - x: line through (0,4)(0,4) and (4,0)(4,0).
Answer: Correct straight line with both intercepts labelled.
Marking: 1 mark line, 1 mark intercepts.

8. [2 marks]
y=x24=0x2=4x=2y = x^2 - 4 = 0 \Rightarrow x^2 = 4 \Rightarrow x = 2 or x=2x = -2.
Answer: x=2,2x = 2, -2

9. [2 marks]
y=(x1)2+2y = (x-1)^2 + 2: minimum at (1,2)(1, 2).
Answer: (1,2)(1, 2)
Teaching note: Vertex form (xh)2+k(x-h)^2 + k has minimum at (h,k)(h,k).

10. [2 marks]
From graph through (0,1)(0,1) and (3,7)(3,7), at x=2x=2, y=5y=5.
Answer: 5


Section C: Function Forms, Gradient, and Simple Modelling

11. [2 marks]
y=2x3y = 2x^3, x=2y=2(8)=16x=2 \Rightarrow y = 2(8) = 16.
Answer: 16

12. [2 marks]
y=3×2xy = 3 \times 2^x, x=3y=3×8=24x=3 \Rightarrow y = 3 \times 8 = 24.
Answer: 24

13. [2 marks]
Gradient = 11241=93=3\frac{11-2}{4-1} = \frac{9}{3} = 3.
Answer: 3

14. [2 marks]
Through (0,2)b=2(0,-2) \Rightarrow b = -2. Through (2,4):4=2a2a=3(2,4): 4 = 2a - 2 \Rightarrow a = 3.
Answer: a=3,b=2a=3, b=-2

15. [2 marks]
C(10)=3.50+0.80(10)=3.50+8=11.50C(10) = 3.50 + 0.80(10) = 3.50 + 8 = 11.50.
Answer: $11.50


Section D: Extended Function Reasoning

16. [2 marks]
g(2)=3g(2) = 3, f(3)=32=9f(3) = 3^2 = 9.
Answer: 9

17. [3 marks]
Pass (0,3): c=3c = 3. Pass (1,6): 1+b+3=6b=21 + b + 3 = 6 \Rightarrow b = 2.
Answer: b=2,c=3b=2, c=3 (1 mark each + 1 for method)

18. [3 marks]
y=x2+4x=(x24x)=(x2)2+4y = -x^2 + 4x = -(x^2 - 4x) = -(x-2)^2 + 4. Max at x=2x=2.
Answer: 2
Marking: 2 marks working, 1 mark answer.

19. [3 marks]
(0,5):k=5(0,5): k=5. (1,15):5a=15a=3(1,15): 5a=15 \Rightarrow a=3.
Answer: k=5,a=3k=5, a=3

20. [3 marks]
P(n)=R(n)C(n)=9n(50+4n)=5n50P(n) = R(n) - C(n) = 9n - (50 + 4n) = 5n - 50.
P(20)=5(20)50=50P(20) = 5(20) - 50 = 50.
Answer: P(n)=5n50P(n)=5n-50, profit $50
Marking: 1 expression, 2 substitution/answer.