Let $D$ be an integral domain. Prove that every automorphism of $D[x]$ is of the form: $\phi_{a,b} : D[x] \rightarrow D[x]$
$f$ $\rightarrow$ $f(ax+b)$
where a is a unit of $D$ and $b \in D$.
Not sure where to exactly jump in on this problem.
Let $D$ be an integral domain. Prove that every automorphism of $D[x]$ is of the form: $\phi_{a,b} : D[x] \rightarrow D[x]$
$f$ $\rightarrow$ $f(ax+b)$
where a is a unit of $D$ and $b \in D$.
Not sure where to exactly jump in on this problem.