$$\vcenter {\offinterlineskip
\def \cc#1{ \hfil #1 \hfil }
\halign {
\tvg \cc {$#$}& #\tv & \cc {$#$} & \cc {$#$}& \cc {$#$}&
\cc {$#$}& \cc {$#$} &#\tv\cr
\noalign {\hrule}
x&& 0&& 2&& 8&
\cr
\noalign {\hrule}
f'(x)&&& -& 0& +&&
\cr
\noalign {\hrule}
\buuucenter {$f(x)$} &&\bbuup{1} &\bbrightddownarrow & \down {0}
&\bbrightuuparrow &\bbuup {2}&
\cr
\noalign {\hrule}
}}
$$