Đáp án:
Giải thích các bước giải:
\(\begin{array}{l}\overline {abcabc} = \overline {abc} \times 1000 + \overline {abc} = \overline {abc} \times \left( {1000 + 1} \right)\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \overline {abc} \times 1001\\\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = \overline {abc} \times 143 \times 7\,\,\,\,\,\,\, \vdots \,\,\,\,7\\ \Rightarrow \overline {abcabc} \,\,\,\,luon\,\,chia\,\,het\,\,cho\,\,7\end{array}\)