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a: 7/8>210/243
b: 11/15<13/14
c: 31/41<313/413
d: 18/53<26/78
a/
2020.2021=(2019+1)(2022-1)=
=2019.2022-2019+2022-1=2019.2022+2>2019.2022
b/
\(4^7=\left(2^2\right)^7=2^{14}< 2^{15}\)
c/
\(199^{20}< 200^{20}=\left(8.25\right)^{20}=\left(2^3.5^2\right)^{20}=2^{60}.5^{40}\)
\(2000^{15}=\left(16.125\right)^{15}=\left(2^4.5^3\right)^{15}=2^{60}.5^{45}\)
\(\Rightarrow2000^{15}=2^{60}.5^{45}>2^{60}.5^{40}>199^{20}\)
d/
\(31^{31}< 32^{31}=\left(2^5\right)^{31}=2^{155}\)
\(17^{39}>16^{39}=\left(2^4\right)^{39}=2^{156}\)
\(\Rightarrow17^{39}=2^{156}>2^{155}>31^{31}\)
Đặt B =\(32^{17}.8^{19}\)
So sánh :\(A=64^{11}.16^{11}\)và \(B=32^{17}.8^{19}\)
TA có :\(A=64^{11}.16^{11}=\left(64.16\right)^{11}=1024^{11}=\left(2^{10}\right)^{11}\)\(=2^{110}\)
\(B=32^{17}.8^{19}=\left(2^5\right)^{17}.\left(2^3\right)^{19}=2^{85}.2^{57}\)\(=2^{142}\)
VÌ A < B ( 2110< 2142)
Nên A < 3217.819
a/ \(63^6< 64^6=\left(8^2\right)^6=8^{12}< 86^{12}\)
b/ \(2^{32}=\left(2^2\right)^{16}=4^{16}\)
\(3^{14}< 3^{16}< 4^{16}\)
\(\Rightarrow2^{32}>3^{14}\)
c/ \(64^{15}< 128^{15}< 128^{30}\)
d/ \(31^{11}>17^{11}\)