Let f:A--->B be a function. Prove that f is surjective if and only if f^(-1)(W) does not equal the empty set for all nonempty sets W of B.
I really do not know what to do with this. Thanks for your help everyone
Let f:A--->B be a function. Prove that f is surjective if and only if f^(-1)(W) does not equal the empty set for all nonempty sets W of B.
I really do not know what to do with this. Thanks for your help everyone