TA có: \(\overline{ab}+\overline{cd}+\overline{eg}\) ⋮11
=>\(\overline{ab}+\overline{cd}+\overline{eg}+9999\cdot\overline{ab}+99\cdot\overline{cd}\) ⋮11
=>\(10000\cdot\overline{ab}+100\cdot\overline{cd}+\overline{eg}\) ⋮11
=>\(\overline{abcdeg}\) ⋮11