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a) \(7^6+7^5-7^4=7^4.7^2+7^4.7+7^4.1\)
\(=7^4.\left(7^2+7-1\right)\)
\(=7^4.55\)
Mà \(55⋮11\Rightarrow7^4.55⋮11\Leftrightarrow7^6+7^5-7^4⋮11\left(đpcm\right).\)
b) \(10^9+10^8+10^7=10^6.10^3+10^6.10^2+10^6.10\)
\(=10^6.\left(10^3+10^2+10\right)\)
\(=10^6.1110\)
Mà \(1110⋮222\Rightarrow10^6.110⋮222\Leftrightarrow10^9+10^8+10^7⋮222\left(đpcm\right).\)
c) \(81^7-27^9-9^{13}=\left(3^4\right)^7-\left(3^3\right)^9-\left(3^2\right)^{13}\)
\(=3^{28}-3^{27}-3^{26}\)
\(=3^{26}.3^2+3^{26}.3+3^{26}.1\)
\(=3^{26}.\left(3^2+3+1\right)\)
\(=3^{24}.3^2.5\)
\(=3^{24}.45\)
Mà \(45⋮45\Rightarrow3^{24}.45⋮45\Leftrightarrow81^7-27^9-9^{13}⋮45\left(đpcm\right).\)
d) \(24^{54}.54^{24}.2^{10}=\left(8.3\right)^{54}.\left(27.2\right)^{24}.2^{10}\)
\(=\left(2^3.3\right)^{54}.\left(3^3.2\right)^{24}.2^{10}\)
\(=\left(2^3\right)^{54}.3^{54}.\left(3^3\right)^{24}.2^{24}.2^{10}\)
\(=2^{162}.3^{54}.3^{72}.2^{34}\)
\(=2^{196}.3^{126}\)
\(=2^{189}.2^7.3^{126}\)
\(=\left[\left(2^3\right)^{63}.\left(3^2\right)^{63}\right].2^7\)
\(=\left(8^{63}.9^{63}\right).2^7\)
\(=72^{63}.2^7\)
Mà \(72^{63}⋮72^{63}\Rightarrow72^{63}.2^7⋮72^{63}\Leftrightarrow24^{54}.54^{24}.2^{10}⋮72^{63}\left(đpcm\right).\)
Bạn tham khảo nhé! Mình không chắc là đúng hay không nữa 
https://hoc24.vn/hoi-dap/question/124418.html
\(24^{54}.54^{24}.2^{10}=\left(2^3.3\right)^{54}.\left(3^3.2\right)^{24}.2^{10}\)\(=2^{3.54}.3^{54}.3^{3.24}.2^{24}.2^{10}\)
\(=2^{162}.3^{54}.3^{72}.2^{72}.2^{24}.2^{10}=2^{162+72+54+10}.3^{54+72}\)\(=2^{298}.3^{126}\).
\(72=3^3.2^3\)
\(72^{63}=\left(3^3.2^3\right)^{63}=3^{189}.2^{189}\)
Như vậy đề bài sai.
a) \(7^6+7^5-7^4\)chia hết cho 11
\(=7^4\left(7^2+7-1\right)\)
\(=7^4.55=7^4.5.11\)chia hết cho 11
b) \(24^{54}.54^{24}.2^{10}\)chia hết cho \(72^{63}\)
\(=\left(2^3.3\right)^{54}.\left(3^3.2\right)^{24}\)
\(=\left(2^3\right)^{54}.3^{54}.\left(3^3\right)^{24}.2^{24}.2^{10}\)
\(=2^{162}.2^{24}.2^{10}.3^{54}.3^{72}\)
\(=2^{196}.3^{126}\)
\(72^{63}=\left(2^3.3^2\right)^{63}\)
\(=\left(2^3\right)^{63}.\left(3^2\right)^{63}=2^{189}.3^{126}\)
Vì \(2^{196}.3^{126}\)chia hết \(2^{189}.3^{126}\)
\(\Rightarrow24^{54}.54^{24}.2^{10}\)chia hết cho\(72^{63}\)
2454.5424.210 = (23.3)54.(2.33)24.210 = 2162.354.224.372.210 = 2196.3126 = 27(2189.3126) = 27.[(23)63.(32)63] = 27.(863.963) = 27.7263 chia hết cho 7263
Tính: (1 - 1/4 ) . (1 - 1/9) . (1 - 1/16) ... (1 - 1/81) . (1 - 1/100)
tham khảo câu b bài 1 ở link này https://olm.vn/hoi-dap/detail/88152567739.html