Exam-style question
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Given functions f: A → B and g: B → C, what is the domain of the composition g ○ f?.
- A.A
- B.B
- C.C
- D.A ∪ C
Model answer
What a good answer should say
- A
Explanation
Why this works
The composition g ○ f applies f first, so its input must come from the domain of f, which is A.
Common mistake
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