Giải thích các bước giải:
a,
$5^{5}-5^{4}+5^{3}$
$= 5^{3}\left ( 5^{2}-5+1 \right )$
$= 5^{3}.21\vdots 7$
b,
$10^{6}-5^{7}$
$= 2^{6}.5^{6}-5^{7}$
$= 5^{6}\left ( 2^{6}-5 \right )$
$= 5^{6}\left ( 64-5 \right )$
$= 5^{6}.59\vdots 59$
c,
$81^{7}-27^{9}-9^{13}$
$= 3^{28}-3^{27}-3^{26}$
$= 3^{24}\left ( 3^{4}-3^{3}-3^{2} \right )$
$= 3^{24}.45\vdots 45$