Exercises
[250]Let \(D,C\) be non-empty sets and \(f:D\to C\) a function. Given \(U\subseteq C\) show that
\[ f(f^{-1}(U)) \subseteq U~ ; \]if \(f\) is surjective show that they are equal; find an example where they are different.
[250]Let \(D,C\) be non-empty sets and \(f:D\to C\) a function. Given \(U\subseteq C\) show that
if \(f\) is surjective show that they are equal; find an example where they are different.