109+108+107=107.(102+10+1)=107.111=106.10.111=106.2.5.111=106.2.555
Vậy 109 + 108 + 107 chia hết cho 555
Ta có :
\(10^9+10^8+10^7=10^7\left(1+10+10^2\right)=10^7\left(1+10+100\right)=10^7.111\)
\(=10^6.10.111=10^6.2.5.111=10^6.2.555\)
Chia hết cho 555 ( ĐPCM)