I’m trying to use \bbox to enclose an expression in a box. However, when doing so within an {align} block and using the & alignment operator, it returns an error:
$$
\begin{align}
\bbox[5px, border: 2px solid red]{f'(x)&=\dfrac{1}{g'(f(x))}} \\\\
\end{align}
$$
{for context, this is how it looks without the alignment operator block:
$$
\begin{align}
\bbox[5px, border: 2px solid red]{f'(x)=\dfrac{1}{g'(f(x))}} \\\\
\end{align}
$$
Any ideas if I’m doing something wrong or if it’s a bug?