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Question
Give an example of a map which is not one-one but onto
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Solution
Let f: R → `[0, oo)`, be a mapping defined by f(x) = |x|
Then, it’s clearly seen that f(x) is not one-one as f(2) = f(–2).
But |x| ≥ 0, so range is `[0, oo].`
Therefore, f(x) is onto.
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