a) 817 - 279 - 913
= (34)7 - (33)9 - (32)13
= 328 - 327 - 326
= 326.(32 - 3 - 1)
= 326.(9 - 3 - 1)
= 325.3.5
= 325.15 chia hết cho 15 (đpcm)
b) 20161000 + 2016999
= 2016999.(2016 + 1)
= 2016999.2017 chia hết cho 2017 (đpcm)
817 - 279 - 913
= (34)7 - (33)9 - (32)13
= 328 - 327 - 326
= 325(33 - 32 - 3)
= 325 . 15
Vậy 817 - 279 - 913 chia hết cho 15
20161000 + 2016999
= 2016999(2016 + 1)
= 2016999 . 2017
Vậy 20161000 + 2016999 chia hết cho 2017.
a) \(81^7-27^9-9^{13}=\left(3^4\right)^7-\left(3^3\right)^9-\left(3^2\right)^{13}=3^{28}-3^{27}-3^{26}=3^{25}\left(3^3-3^2-3\right)=3^{25}.15⋮15\)
\(\Rightarrowđpcm\)
b) \(2016^{1000}+2016^{999}=2016^{999}.\left(2016+1\right)=2016^{999}.2017⋮2017\)
\(\Rightarrowđpcm\)
