Referring to Lang's Algebra p. 181, let $A$ be a factorial ring and $K$ its field of fractions. It is clear by definition, that the content of $f(x) \in K[x]$ is an element of $A$.
In the beginning of the paragraph above Theorem 2.1 it is mentioned that if $b \in K, \, b \neq 0$, then $cont(bf)=b \cdot cont(f)$. But then $b \cdot cont(f)$ might not be inside $A$.
Is this a typo or am i missing something?