ta có abc.9=6abc a.900+b.90+c.9=6000+ a.100+b.10+c a.800+b.80+c.8 = 6000 8(a.100+b.10+c)=6000 abc=6000:8=750 Vậy số tự nhiên abc = 750
abc . 9 = 6abc
abc . 9 = 6000 + abc
abc . 8 = 6000
abc = 750
\(\Rightarrow\text{abc x 9 = 6abc }\)
\(\Rightarrow\text{abc x 9 = 6000 + abc }\)
\(\Rightarrow\text{abc x 8 = 6000 }\)
\(\Rightarrow\text{abc = 6000 : 8 }\)
\(\Leftrightarrow\text{abc = 750 }\)