f(g(x)): Error Analysis & Misconceptions
Mathematics
GCSE Foundation
13 questions
~26 mins
1 views0 downloads
About This Worksheet
A worksheet focusing on understanding and avoiding common errors when calculating composite functions f(g(x)). Includes practice, reasoning, and error analysis for GCSE Foundation students.
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f(g(x)): Error Analysis & Misconceptions
Subject: MathematicsGrade: GCSE Foundation
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Untitled Worksheet
Grade GCSE Foundation
A
Introduction
1.
Recall the general form of a composite function f(g(x)). Write the expression for f(g(x)) if f(x) = 2x + 3 and g(x) = x^2 - 1.
[3 marks]2.
Explain in your own words what the composite function f(g(x)) represents.
[2 marks]B
Fluency & Practice
Answer all questions. Show your working in the grid spaces provided.
1.
Calculate f(g(2)) for f(x) = 3x - 4 and g(x) = x + 5.
[3 marks]2.
If f(x) = x^2 + 2 and g(x) = 4 - x, find f(g(3)).
[3 marks]3.
Given f(x) = 2x + 1 and g(x) = x/2, what is f(g(8))?
[3 marks]C
Problem Solving & Reasoning
Answer all questions clearly, showing your reasoning.
1.
The functions are f(x) = 5x - 2 and g(x) = x^2 + 1. Find a simplified expression for f(g(x)).
[4 marks]2.
If the composite function f(g(x)) has a constant value for all x, what does this imply about the functions f and g?
[4 marks]3.
Given f(x) = 4x + 7 and g(x) = 3x - 5, find f(g(4)). Show your working.
[4 marks]D
Real-world Applications
Solve the questions based on the context provided.
1.
A car rental company charges a fixed fee plus a rate per mile. The total cost C(x) = 50 + 0.2x. If g(x) models the miles driven as x, and f(x) models the total cost after applying a discount function h(x)=x-10 on miles driven, write an expression for the total cost after the discount, expressed as a composite function.
[4 marks]E
Challenge & Extension
Attempt these challenging questions. Show detailed working.
1.
Given functions f(x) = x^3 and g(x) = 2x + 1, find the expression for f(g(g(2))).
[4 marks]2.
Identify and correct the mistake in the following student solution: f(x) = x+4, g(x) = x^2, compute f(g(3)) and the student wrote: f(g(3))= (3)^2+4=9+4=13, but claims the answer is 16.
[4 marks]F
Mixed Review
Answer these questions to reinforce understanding of f(g(x)).
1.
Construct a function g(x) and a function f(x) such that f(g(x)) = 3x + 2, but neither f nor g is linear.
[4 marks]2.
Plot the graph of y=2x on the provided grid. Then, describe how the graph of y=f(g(x)) might look if f and g are both linear functions with slopes of 2 and 3 respectively.
[4 marks]Quick Actions
What is Remix?
Create a new worksheet based on this one. Change the grade level, topic, number of questions, or difficulty - then generate a fresh version.
- • Change grade level (Grade 6 → Grade 7)
- • Swap topics (Harry Potter → Macbeth)
- • Add more questions (10 → 15)
- • Adjust difficulty
Details
- Created
- 1/1/2026
- Updated
- 1/1/2026
- Type
- worksheet