alleryFor f(x) = 2x from N to N, the function is:
ABoth one-one and onto
BNeither of the two
COne-one, not onto
DOnto, not one-one
Answer & Solution
Correct answer: C. One-one, not onto
1. Doubling sends distinct naturals to distinct naturals, so f is one-one.
2. No natural number x gives 2x = 1, so 1 has no preimage.
3. So f is one-one but not onto.
_Source: syllabus Mathematics Part I, Chapter 1, Relations and Functions._
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