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a: \(17A=\dfrac{17^{19}+17}{17^{19}+1}=1+\dfrac{16}{17^{19}+1}\)
\(17B=\dfrac{17^{18}+17}{17^{18}+1}=1+\dfrac{16}{17^{18}+1}\)
mà 17^19+1>17^18+1
nên A<B
b: \(2C=\dfrac{2^{2021}-2}{2^{2021}-1}=1-\dfrac{1}{2^{2021}-1}\)
\(2D=\dfrac{2^{2022}-2}{2^{2022}-1}=1-\dfrac{1}{2^{2022}-1}\)
2^2021-1<2^2022-1
=>1/2^2021-1>1/2^2022-1
=>-1/2^2021-1<-1/2^2022-1
=>C<D
Ta có F < 1 nên
\(\dfrac{13580}{34569}< 1< \dfrac{13580+\left(-1\right)}{34569+\left(-1\right)}=\dfrac{13579}{34568}\)<\(\dfrac{13579}{34567}\)
Từ đó suy ra \(\dfrac{13580}{34569}< \dfrac{13579}{34567}\)hay\(\dfrac{13579}{34567}>\dfrac{13580}{34569}\)
Vậy E > F
B=\(\dfrac{10^9+1}{10^{10}+1}< \dfrac{10^5+1+9}{10^{10}+1+9}=\dfrac{10^9+10}{10^{10}+10}=\dfrac{10.\left(10^8+1\right)}{10\left(10^9+1\right)}\)
= A
\(A=\dfrac{2}{1.2}+\dfrac{2}{2.3}+\dfrac{2}{3.4}+...+\dfrac{2}{99.100}\)
\(A=2\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+\dfrac{1}{3.4}+...+\dfrac{1}{99.100}\right)\)
\(A=2\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{98}-\dfrac{1}{99}+\dfrac{1}{99}-\dfrac{1}{100}\right)\)
\(A=2\left(1-\dfrac{1}{100}\right)\)
\(A=2.\dfrac{99}{100}\)
\(A=\dfrac{99}{50}\)
\(\dfrac{2004.2005-1}{2004.2005}=1-\dfrac{1}{2004.2005}\)
\(\dfrac{2005.2006-1}{2004.2006}=1-\dfrac{1}{2005.2006}\)
\(Vì\dfrac{1}{2004.2005}>\dfrac{1}{2005.2006}\Rightarrow1-\dfrac{1}{2004.2005}< 1-\dfrac{1}{2005.2006}\Rightarrow\dfrac{2004.2005-1}{2004.2005}< \dfrac{2005.2006-1}{2004.2006}\)
tham khảo:
https://olm.vn/hoi-dap/detail/56325533229.html
3.13579/34567 = 40737/34567 = 34567+6170/34567
3.13580/34569 = 40740/34569 = 34569+6171/34569
vì : 34567+6170/34567 < 34569+6171/34569
nên: 3.13579/34567 < 3.13580/34569
vậy: 13579/34567 < 13580/34569