Giải thích các bước giải:
$a)7^6+7^4-7^4\\ =7^4(7^2+7-1)\\ =7^4.55 \ \vdots \ 55\\ b)81^7-27^9+3^{29}\\ =(3^4)^7-(3^3)^9+3^{29}\\ =3^{4.7}-3^{3.9}+3^{29}\\ =3^{28}-3^{27}+3^{29}\\ =3^{27}(3-1+3^2)\\ =3^{27}(2+9)\\ =3^{27}.11\\ =3^{26}.33 \ \vdots \ 33\\ c)8^{12}-2^{33}-2^{30}\\ =(2^3)^{12}-2^{33}-2^{30}\\ =2^{3.12}-2^{33}-2^{30}\\ =2^{36}-2^{33}-2^{30}\\ =2^{30}(2^{6}-2^{3}-1)\\ =2^{30}(64-8-1)\\ =2^{30}.55 \ \vdots \ 55\\ d)10^9+10^8+10^7\\\ =10^7(10^2+10+1)\\ =10^7(100+10+1)\\ =10^7.111\\ =10^6.2.5.111\\ =10^6.2.555 \ \vdots \ 555$
