so sánh
1920 và 98 . 516
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\(A=\dfrac{19^{20}+5}{19^{20}-8}=\dfrac{19^{20}-8+13}{19^{20}-8}=1+\dfrac{13}{19^{20}-8}\)
\(B=\dfrac{19^{21}-7+13}{19^{21}-7}=1+\dfrac{13}{19^{21}-7}\)
Mà \(19^{21}-7>19^{20}-8\)
=> \(A>B\)
Bg
Ta có: \(\frac{-304}{303}+\frac{1}{303}\)\(=-1\)và \(\frac{-517}{516}+\frac{1}{516}\)\(=-1\)
Vì \(\frac{1}{303}>\frac{1}{516}\)nên \(\frac{-304}{303}< \frac{-517}{516}\)
Vậy \(\frac{-304}{303}< \frac{-517}{516}\).
\(\frac{339}{322}\)và \(\frac{338}{321}\)
Ta có : \(\frac{339}{322}-1=\frac{17}{322};\frac{338}{321}-1=\frac{17}{321}\).
Vì \(\frac{17}{322}< \frac{17}{321}\)nên \(\frac{339}{322}< \frac{338}{321}\).
\(\frac{2017}{2014}\)và \(\frac{2018}{2015}\)
Ta có : \(\frac{2017}{2014}-1=\frac{3}{2014};\frac{2018}{2015}-1=\frac{3}{2015}\)
Vì \(\frac{3}{2014}>\frac{3}{2015}\)nên \(\frac{2017}{2014}>\frac{2018}{2015}\).
\(\frac{511}{514}\)và \(\frac{513}{516}\)
Ta có : \(1-\frac{511}{514}=\frac{3}{514};1-\frac{513}{516}=\frac{3}{516}\)
Vì \(\frac{3}{514}>\frac{3}{516}\)nên \(\frac{511}{514}< \frac{513}{516}\).
\(\frac{3005}{3000}\)và \(\frac{3010}{3005}\)
Ta có : \(\frac{3005}{3000}-1=\frac{5}{3000};\frac{3010}{3005}-1=\frac{5}{3005}\)
Vì \(\frac{5}{3000}>\frac{3}{3005}\)nên \(\frac{3005}{3000}>\frac{3010}{3005}\).
~ Chúc bn hok tốt ~
\(\dfrac{19}{19}\) = 1 < \(\dfrac{2005}{2004}\) vậy \(\dfrac{19}{19}\) < \(\dfrac{2005}{2004}\)
\(\dfrac{72}{73}\) = 1 - \(\dfrac{1}{73}\)
\(\dfrac{98}{99}\) = 1 - \(\dfrac{1}{99}\)
Vì \(\dfrac{1}{73}\) > \(\dfrac{1}{99}\) nên \(\dfrac{72}{73}\) < \(\dfrac{98}{99}\)
\(C-D=\dfrac{\left(98^{99}+1\right)\left(98^{88}+1\right)-\left(98^{89}+1\right)\left(98^{98}+1\right)}{\left(98^{89}+1\right)\left(98^{88}+1\right)}\)
\(=\dfrac{98^{187}+98^{99}+98^{88}+1-98^{197}-98^{89}-98^{98}-1}{\left(98^{89}+1\right)\left(98^{88}+1\right)}\)
\(=\dfrac{98^{99}-98^{98}+98^{88}-98^{89}}{\left(98^{89}+1\right)\left(98^{88}+1\right)}=\dfrac{98^{98}\left(98-1\right)-98^{88}\left(98-1\right)}{\left(98^{89}+1\right)\left(98^{88}+1\right)}\)
\(=\dfrac{97.98^{98}-97.98^{88}}{\left(98^{89}+1\right)\left(98^{88}+1\right)}=\dfrac{97.98^{88}\left(98^{10}-1\right)}{\left(98^{89}+1\right)\left(98^{88}+1\right)}>0\)
\(\Rightarrow C>D\)
có ba trường hợp
do mih ko rảnh nên ko trả lời chính xác đâu nha
th1 : <
th2: >
th3: =