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\theoremstyle{definition}
\newtheorem*{cau1}{Câu 1}
\newtheorem*{cau2}{Câu 2}
\newtheorem*{cau3}{Câu 3}
\newtheorem*{cau4}{Câu 4}
\newtheorem*{cau5}{Câu 5}
\newtheorem*{cau6}{Câu 6}
\newtheorem*{cau7}{Câu 7}
\newtheorem*{cau8}{Câu 8}
\newtheorem*{cau9}{Câu 9}
\newtheorem*{cau10}{Câu 10}
\newtheorem*{cau11}{Câu 11}
\newtheorem*{cau12}{Câu 12}

\begin{document}

\begin{center}
\noindent \textbf{BÀI TẬP VỀ ĐỊNH LÝ PY-TA-GO}\\
\end{center}

\begin{cau1}
Tìm độ dài x trên hình sau:\\
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\end{cau1}

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