so sánh 88/99 ,777/888,6666/7777,55555/66666
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1.M = 1992 . 19911991 - 1991 . 1992
M = 1992 . 1991 . 10001 - 1991 . 1992
M = 10001
Bg
Ta có: \(M=\frac{-2020}{55555^{66666}}\)và \(N=\frac{2020}{-66666^{55555}.11111^{11111}}\)
Xét \(M=\frac{-2020}{55555^{66666}}\):
=> \(M=\frac{-2020}{\left(11111.5\right)^{11111.6}}\)
=> \(M=\frac{-2020}{11111^{11111.6}.5^{11111.6}}\)
=> \(M=\frac{-2020}{11111^{11111.6}.5^{6^{11111}}}\)
=> \(M=\frac{-2020}{11111^{11111.6}.15625^{11111}}\)
Xét \(N=\frac{2020}{-66666^{55555}.11111^{11111}}\):
=> \(N=\frac{-2020}{\left(11111.6\right)^{11111.5}.11111^{11111}}\)
=> \(N=\frac{-2020}{11111^{11111.5}.6^{11111.5}.11111^{11111}}\)
=> \(N=\frac{-2020}{11111^{11111.5}.11111^{11111}.6^{11111.5}}\)
=> \(N=\frac{-2020}{11111^{11111.5+}^{11111}.6^{11111.5}}\)
=> \(N=\frac{-2020}{11111^{11111.6}.6^{11111.5}}\)
=> \(N=\frac{-2020}{11111^{11111.6}.7776^{11111}}\)
Vì 777611111 < 1562511111 nên \(M=\frac{-2020}{11111^{11111.6}.15625^{11111}}\)> \(N=\frac{-2020}{11111^{11111.6}.7776^{11111}}\)
Vậy M > N
Ta có:
\(222^{777}=111^{777}\cdot2^{777}\) \(\left(1\right)\)
\(777^{222}=111^{222}.7^{222}\) \(\left(2\right)\)
Ta lại có:
\(2^{777}=\left(2^7\right)^{111}=128^{111}\) \(\left(3\right)\)
\(7^{222}=\left(7^2\right)^{111}=49^{111}\) \(\left(4\right)\)
Từ \(\left(1\right),\left(2\right),\left(3\right)\) và \(\left(4\right)\)
\(\Rightarrow222^{777}>777^{222}\)
Ta có: 777333 = 777(3.111) = (7773)111 = 2331111
333777 = 333(7.111) = (3337)111 = 2331111
=> 2331 = 2331 mà 2331111 = 2331111 hay 777333 = 333777
222^777 = (2 . 111) ^777 = 2^777 . 111^777
= (2^7)^111 . (111^7)^111
777^222. = (7 . 111)^222 = 7^222 . 111^222
= (7^2)^111 . (111^2)^111
So sánh ta thấy:
2^7 > 7^2
111^7 > 111^2
==> (2^7)^111 . (111^7)^111 > (7^2)^111 . (111^2)^111
==> 222^777 > 777^222
Ta có : 222^777=(2.111)^7.111=128^111.(111^7)^111
777^222=(7.111)^2.111=49^111.(111^2)^111
Vì 128^111>49^111
(111^7)^111>(111^2)^111
=>222^777>777^222