Practice question · Select all that apply
Let f(n) = 2n with domain and codomain the integers. Select every integer that IS in the image of f.
Hints
- An integer is in the image when some integer input produces it.
- Solve 2n = k and ask whether n comes out an integer.
Show the answer
- B. -4
- C. 0
- D. 10
Why
-4, 0 and 10 come from n = -2, 0 and 5. But 2n = 3 needs n = 1.5, which is not in the domain, and likewise for 7. The image is exactly the even integers, so f is not surjective onto the integers.
Practise Functions as Mappings
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