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a) 5^23 và 6 . 5^22
Ta có: 5^23 = 5^22 . 5
Vì 5 < 6 nên 5^23 < 6 . 5^22
b) 7 . 2^13 và 2^16
Ta có: 2^16 = 2^13 . 2^3 = 2^13 . 8
Vì 7 < 8 nên 7 . 2^13 < 2^16
c) 21^15 và 27^5 . 49^8
Ta có: 21^15 = (3.7)^15 = 3^15 . 7^15
27^5 . 49^8 = (3^3)^5 . (7^2)^8 = 3^15 . 7^16
Vì 7^15 < 7^16 nên 21^15 < 27^5 . 49^8
Câu 1.9920và 999910
=(992)10=980110
Vậy 980110<999910 suy ra 9920<999910
Câu 2. 3500và 7300
3500=(35)100=243100
7300=(73)100=343100
Vậy 243100<343100 => 3500<7300
\(2^{x-3}=128\Leftrightarrow2^{x-3}=2^7\Rightarrow x-3=7\Leftrightarrow x=10\)
\(\left(x+6\right)^4=4096\Leftrightarrow\left(x+6\right)^4=2^{12}=\left(2^3\right)^4=8^4\Rightarrow x+6=8\Leftrightarrow x=2\)
\(2^{2018}=\left(2^4\right)^{504}.2^2==16^{504}.4< 16^{900}\\ \)
\(17^{20}>16^{20}=\left(4^2\right)^{20}=4^{40}\)
\(3^{444}=\left(3^4\right)^{111}=81^{111}>64^{111}=\left(4^3\right)^{111}=4^{333}\\ \)
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\(\dfrac{7^{45}}{7}=7^{44}\)
\(49.7^{20}=7^2.7^{20}=7^{22}\)
\(\Rightarrow\dfrac{7^{45}}{7}=7^{44}>7^{22}=49.7^{20}\)
745 : 7 23 = 722
49 \(\times\) 720 = 72 \(\times\) 720 = 722
745 : 723 = 49 \(\times\) 720