\begin{tikzpicture}
\draw[->,>=stealth,semithick] (-3.5,0)--(3.5,0)node[above]{$x$}; %trục x
\draw[->,>=stealth,semithick] (0,-3.5)--(0,2.5)node[right]{$y$}; %trục y
\draw (0,0)node[below right]{O}; %Gốc tọa độ
\draw[red,very thick,domain=-2:2] plot(\x,{\x*\x})node[right]{$y=x^2$};
\end{tikzpicture}