\(\overline{abc}+\overline{den}⋮37\Rightarrow\hept{\begin{cases}\overline{abc⋮}37\\\overline{den⋮}37\end{cases}}\)
\(\Rightarrow\overline{abc}.1000+\overline{den}⋮37\)
\(\Rightarrow\overline{abcden}⋮37\)
\(\overline{abcden}=1000\times\overline{abc}+\overline{den}=999\times\overline{abc}+\left(\overline{abc}+\overline{den}\right)=37\times27\times\overline{abc}+\left(\overline{abc}+\overline{den}\right)\)
Vì 37X27Xabc chia hết cho 37 vạ abc+den chia hết cho 37 nên abcden chia hết cho 37(ĐPCM)
