Give an example of a map

which is not one-one but onto

Dear Student

Let f: R → [0, ∞), 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, ∞].
Thus, f (x) is onto.


Thanks