For this, we need to find constants $C$ and $k$ such that $|f(x)| \leq C|x^n|$ for all $x > k$.
Let $k = \max\{1, |a_0|, |a_1|, \ldots, |a_{n-1}|\}$. Then for $x > k$, we have:
\begin{align*}
|f(x)| &= |a_nx^n + a_{n-1}x^{n-1} + \ldots + a_1x + a_0| \\
&\leq
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