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11 tháng 11 2017

Ta có :

\(\left(\frac{16}{25}\right)^{10}=\left(\frac{4^2}{5^2}\right)^{10}=\left(\frac{4}{5}\right)^{2.10}=\left(\frac{4}{5}\right)^{20}\)

\(\left(\frac{3}{7}\right)^{40}=\left(\frac{3}{7}\right)^{2.20}=\left(\frac{3^2}{7^2}\right)^{20}=\left(\frac{9}{49}\right)^{20}\)

Vì 20 = 20 và \(\frac{4}{5}>\frac{9}{49}\)nên \(\left(\frac{4}{5}\right)^{20}>\left(\frac{9}{49}\right)^{20}\)

Vậy \(\left(\frac{16}{25}\right)^{10}>\left(\frac{3}{7}\right)^{40}\)

31 tháng 5

Ta có: \(3A=\frac{3^{19}+6}{3^{19}+10}=\frac{3^{19}+10-4}{3^{19}+10}=1-\frac{4}{3^{19}+10}\)

\(3B=\frac{3^{18}+6}{3^{18}+10}=\frac{3^{18}+10-4}{3^{18}+10}=1-\frac{4}{3^{18}+10}\)

Ta có: \(3^{19}+10>3^{18}+10\)

=>\(\frac{4}{3^{19}+10}<\frac{4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}>\frac{-4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}+1>\frac{-4}{3^{18}+10}+1\)

=>3A>3B

=>A>B

31 tháng 5

Ta có: \(3A=\frac{3^{19}+6}{3^{19}+10}=\frac{3^{19}+10-4}{3^{19}+10}=1-\frac{4}{3^{19}+10}\)

\(3B=\frac{3^{18}+6}{3^{18}+10}=\frac{3^{18}+10-4}{3^{18}+10}=1-\frac{4}{3^{18}+10}\)

Ta có: \(3^{19}+10>3^{18}+10\)

=>\(\frac{4}{3^{19}+10}<\frac{4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}>\frac{-4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}+1>\frac{-4}{3^{18}+10}+1\)

=>3A>3B

=>A>B

31 tháng 5

Ta có: \(3A=\frac{3^{19}+6}{3^{19}+10}=\frac{3^{19}+10-4}{3^{19}+10}=1-\frac{4}{3^{19}+10}\)

\(3B=\frac{3^{18}+6}{3^{18}+10}=\frac{3^{18}+10-4}{3^{18}+10}=1-\frac{4}{3^{18}+10}\)

Ta có: \(3^{19}+10>3^{18}+10\)

=>\(\frac{4}{3^{19}+10}<\frac{4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}>\frac{-4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}+1>\frac{-4}{3^{18}+10}+1\)

=>3A>3B

=>A>B

31 tháng 5

Ta có: \(3A=\frac{3^{19}+6}{3^{19}+10}=\frac{3^{19}+10-4}{3^{19}+10}=1-\frac{4}{3^{19}+10}\)

\(3B=\frac{3^{18}+6}{3^{18}+10}=\frac{3^{18}+10-4}{3^{18}+10}=1-\frac{4}{3^{18}+10}\)

Ta có: \(3^{19}+10>3^{18}+10\)

=>\(\frac{4}{3^{19}+10}<\frac{4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}>\frac{-4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}+1>\frac{-4}{3^{18}+10}+1\)

=>3A>3B

=>A>B

31 tháng 5

Ta có: \(3A=\frac{3^{19}+6}{3^{19}+10}=\frac{3^{19}+10-4}{3^{19}+10}=1-\frac{4}{3^{19}+10}\)

\(3B=\frac{3^{18}+6}{3^{18}+10}=\frac{3^{18}+10-4}{3^{18}+10}=1-\frac{4}{3^{18}+10}\)

Ta có: \(3^{19}+10>3^{18}+10\)

=>\(\frac{4}{3^{19}+10}<\frac{4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}>\frac{-4}{3^{18}+10}\)

=>\(\frac{-4}{3^{19}+10}+1>\frac{-4}{3^{18}+10}+1\)

=>3A>3B

=>A>B

30 tháng 5

Ta có; \(3A=\frac{3^{19}+6}{3^{19}+10}=\frac{3^{19}+10-4}{3^{19}+10}=1-\frac{4}{3^{19}+10}\)

\(3B=\frac{3^{18}+6}{3^{18}+10}=\frac{3^{18}+10-4}{3^{18}+10}=1-\frac{4}{3^{18}+10}\)

Ta có: \(3^{19}+10>3^{18}+10\)

=>\(\frac{4}{3^{19}+10}<\frac{4}{3^{18}+10}\)

=>\(-\frac{4}{3^{19}+10}>-\frac{4}{3^{18}+10}\)

=>\(-\frac{4}{3^{19}+10}+1>-\frac{4}{3^{18}+10}+1\)

=>3A>3B

=>A>B