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Ta có:
\(24^{54}.54^{24}.2^{10}=\left(2^3.3\right)^{54}.\left(3^3.2\right)^{24}.2^{10}\)
\(=\left(2^3\right)^{54}.\left(3^3.2\right)^{24}.2^{10}\)
\(=2^{162}.3^{54}.3^{72}.2^{24}.2^{10}\)
\(=2^{196}.3^{126}\) (1)
Lại có:
\(72^{63}=\left(2^3.3^2\right)^{63}=2^{189}.3^{126}\)(2)
Từ (1) và (2) ⇒ \(24^{54}.54^{24}.2^{10}⋮72^{63}\)
3^n+2 - 2^n+2 + 3^n - 2^n = (3n+2+3n)+(-2n+2-2n)
=3n.(32+1)-2n.(22+1)
=3n.10-2n.5
=3n.10-2n-1.2.5
=3n.10-2n-1.10
=10.(3n-2n-1)
Vậy 3^n+2 - 2^n+2 + 3^n - 2^n chia hết cho 10
a, \(81^7-27^9-9^{13}\)
\(=3^{28}-3^{27}-3^{26}\)
\(=3^{22}\left(3^6-3^5-3^4\right)\)
\(=3^{22}\times405⋮405\)
\(2^{54}.54^{24}.2^{10}\)chia hết \(72^{63} \)
\(2^{54}.54^{24}.2^{10}\)=\((2^3.3)^{54}.(3^3.2)^{24}.2^{10}\)
=\((2^3)^{54}.3^{54}.(3^3)^{24}.2^{24}2^{10}\)
= \(2^{162}.2^{24}.2^{10}.3^{54}.3^{72}
\)
=\(2^{196}.3^{126}\)
\(72^{63}
\)=\((2^3.3^2)^{63}\)
=\((2^3)^{63}.(3^2)^{63}=2^{189}.3^{126}\)
Vì \(2^{196}.3^{126}\)chia hết \(2^{189}.3^{126}\)\(24^{54}.54^{24}.2^{10}\)
\(\Rightarrow \)\(24^{54}.54^{24}.2^{10}\)chia hết \(72^{63}
\)(dpcm)
\(\frac{1}{99}-\frac{1}{99.98}-\frac{1}{98.97}-....-\frac{1}{3.2}\)
=\(\frac{1}{99}-\left(\frac{1}{2.3}+\frac{1}{3.4}+....+\frac{1}{98.99}\right)\)
=\(\frac{1}{99}-\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{98}-\frac{1}{99}\right)\)
=\(\frac{1}{99}-\left(\frac{1}{2}-\frac{1}{99}\right)\)
=\(\frac{1}{99}-\frac{97}{198}\)
=\(\frac{-95}{198}\)
\(24^{54}.54^{24}.2^{10}\\ =8^{54}.3^{54}.27^{54}.2^{54}.2^{10}\)
\(=2^{162}.3^{54}.3^{72}.2^{54}.2^{10}\\
=2^{226}.3^{126}\\
=2^{3.63+37}.3^{2.63}\\
=8^{63}.9^{63}.2^{37}\\
=72^{63}.2^{37}\)
Dễ thấy \(72^{63}.2^{37}⋮̸72^{63}\)
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