Solution
= Solution
The <image of a function> is the <set> of values actually attained as its argument ranges over its <domain of a function>:
$$
\boxed{\operatorname{im}f=f(A)=\{f(a):a\in A\}=\{b\in B:\exists a\in A,\ f(a)=b\}.}
$$
It is a <subset> of the <codomain> $B$, and need not equal $B$.