Question

chung minh abc ;bang 2deg thi abcdeg chia het cho23

 

 

Answer 1

abcdeg = 1000 x abc + deg = 1000 x 2 x deg + deg = 2001 x deg = 87 x 23 x deg chia hết cho 23

Answer 2

\(\overline{abc}=2\overline{def}\Rightarrow\overline{abcdef}=1000\overline{abc}+\overline{def}=2000\overline{def}+\overline{def}=2001\overline{def}=23\cdot87\overline{def}\)

\(23⋮23\Rightarrow23\cdot87\overline{def}⋮23\Rightarrow\overline{abcdef}⋮23\)