Solution (source code)

= Solution

Since $1\leq t\leq b$ and $c\geq0$,
$$
b^{-c}\leq t^{-c}\leq1.
$$
Taking suprema gives
$$
\boxed{b^{-c}\|f\|_\infty\leq\|f\|_c\leq\|f\|_\infty}.
$$
\b[Thus the weighted norm and the usual <uniform norm> are <equivalent norms>.]