Proving $f(C) \setminus f(D) \subseteq f(C \setminus D)$ and disproving equality Let $f: A\longrightarrow B$ be a function. 
1)Prove that for any two sets, $C,D\subseteq A$ , we have $f(C) \setminus f(D)\subseteq f(C\setminus D)$.
2)Give an example of a function $f$, and sets $C$,$D$, for which $f(C) \setminus f(D) \neq f(C\setminus D)$
First time exposed to sets.. how would I go about proving this? What assumptions should I make?

This links to a resource of selected attempts to solutions for exercises of Terence Tao's Analysis I (2006) 1E. A proof for $f(C)\backslash f(D) \subseteq f(C \backslash D)$ and $f \hspace{0.2cm} \text{injective} \rightarrow f(C)\backslash f(D) = f(C \backslash D)$ can be found there.
