\begin{enumerate}
\item On a : $\mathcal{D}_f=\intervOO{-\infty}{\dfrac{2}{3}}\cup\intervOO{-\dfrac{2}{3}}{+\infty}$ et :
\begin{center}
\begin{tikzpicture}
\tkzTabInit[lgt=3,color,colorL=violet!20,colorC=violet!20,colorV=violet!20]{$x$/1,$2-3x$/1,$(2-3x)^2$/1,$\dfrac{1}{(2-3x)^2}$/1,$\dfrac{-3}{(2-3x)^2}$/1}{$-\infty$,$-\dfrac{2}{3}$,$+\infty$}
\tkzTabVar{+/,-D+/ /,-/}
\tkzTabVar{+/,-D-/ /,+/}
\tkzTabVar{-/,+D+/ /,-/}
\tkzTabVar{+/,-D-/ /,+/}
\end{tikzpicture}
\end{center}

\item On a : $\begin{aligned}[t]
(x-2)^2-4\geqslant0 &  \Longleftrightarrow x^2-4x+4-4\geqslant0\\
& \Longleftrightarrow x(x-4)\geqslant0
\end{aligned}$

Donc $\mathcal{D}_g=\intervOF{-\infty}{0}\cup\intervFO{4}{+\infty}$ et :

\begin{center}
\begin{tikzpicture}
\tkzTabInit[lgt=3,espcl=3,color,colorL=violet!20,colorC=violet!20,colorV=violet!20]{$x$/1,$x^2-4x$/1,$\sqrt{x^2-4x}$/1}{$-\infty$,$0$,$4$,$+\infty$}
\tkzTabVar{+/,-H/,-/{},+/}
\tkzTabVar{+/,-H/,-/{},+/}
\end{tikzpicture}
\end{center}
\end{enumerate}