Chứng minh rằng:10^9+10^8+10^7 chia hết cho 555

${10}^9+{10}^8+{10}^7⋮555$ 

Ta có ${10}^9+{10}^8+{10}^7={10}^6\cdot \left({10}^3+{10}^2+10\right)={10}^6.1110={10}^6\mathrm{.555.2}⋮555$ 

Vậy ${10}^9+{10}^8+{10}^7⋮555$