165 + 215 = (24)5 + 215 = 2(4.5) + 215 = 220 + 215 = 215 ( 25 + 1) = 215 . (32 + 1 ) = 33 . 215
chia hết cho 33
b, 81^ 7 - 27 ^9 - 9 ^13 = ( 3 ^4 ) ^ 7 - (3^3 ) ^ 9 - (3^2)^13 = 3^28 - 3 ^27 - 3^26
= 3^ 26+ ( 3^2 - 3 - 1 ) = 3^26 . 5 = 3^22 . 3^4 . 5 = 3^22 . 81.5 = 3^ 22. 405 chia hết cho 405
76+75-74 chia hết cho 55
76+75-74=74(72+7-1)=74.55
=>76+75-74 chia hết cho 55
817-279-913 chia hết cho 405
817-279-913=328-327-326=322(36-35-34)=322.405
=>817-279-913 chia hết cho 405
165+215 chia hết cho 33
165+215=220+215=215(25+1)=215.33
=>165+215 chia hết cho 33
Trả lời
\(7^6+7^5-7^4=7^4\left(7^2+7-1\right)=7^4\cdot\left(49+7-1\right)=7^4\cdot55⋮55\)
\(81^7-27^9-9^{13}=3^{28}-3^{27}-3^{26}\)
\(=3^{26}\left(9-3-1\right)=3^{26}\cdot5=3^{22}\cdot405⋮405\)
\(16^5+2^{15}=2^{20}+2^{15}=2^{15}\cdot33⋮33\)
