a) \(5^5-5^4+5^3=5^3.\left(5^2-5+1\right)=5^3.21⋮7\)
\(\Rightarrow5^5-5^4+5^3⋮7\left(đpcm\right)\)
b) \(7^6+7^5-7^4=7^4.\left(7^2+7-1\right)=7^4.55⋮11\)
\(\Rightarrow7^6+7^5-7^4⋮11\left(đpcm\right)\)
a) => 5^5 - 5^4 + 5^3 = 5^3 ( 5^2 - 5 + 1 )
= 5^3 . 21 chia hết cho 7
b) => 7^6 + 7^5 - 7^4 = 7^4 ( 7^2 + 7 + 1 )
= 7^4 . 55 chia hết cho 11
a) 55−54+53=53.(52−5+1)=53.21⋮7
⇒55−54+53⋮7(đpcm)
b) 76+75−74=74.(72+7−1)=74.55⋮11
⇒76+75−74⋮11