Giải thích các bước giải:
Ta có:
\(\begin{array}{l}
102\,\, \vdots \,\,102\\
\Rightarrow 102\overline {ab} \,\, \vdots \,\,102\\
\left( {2\overline {ab} - \overline {cd} } \right)\,\, \vdots \,\,102\\
\Rightarrow \left[ {102\overline {ab} - \left( {2\overline {ab} - \overline {cd} } \right)} \right]\,\, \vdots \,\,102\\
\Leftrightarrow \left( {102\overline {ab} - 2\overline {ab} + \overline {cd} } \right)\,\, \vdots \,\,102\\
\Leftrightarrow \left( {100\overline {ab} + \overline {cd} } \right)\,\, \vdots \,\,102\\
\Leftrightarrow \left( {\overline {ab00} + \overline {cd} } \right)\,\, \vdots \,\,102\\
\Rightarrow \overline {abcd} \,\, \vdots \,\,102
\end{array}\)
