So sánh gt của (192009 + 52009)2010 va (192010 + 52010)2009
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Trước tiên ta có: \(\sqrt[2009]{19^{2009}+5^{2009}}>\sqrt[2009]{19^{2009}}=19\)
và \(\sqrt[2009]{19^{2009}+5^{2009}}>\sqrt[2009]{5^{2009}}=5\)
Ta có: \(\sqrt[2009]{A}=\left(19^{2009}+5^{2009}\right)\sqrt[2009]{19^{2009}+5^{2009}}\)
\(\sqrt[2009]{B}=19^{2010}+5^{2010}\)
\(\Rightarrow\sqrt[2009]{A}-\sqrt[2009]{B}=\left(19^{2009}+5^{2009}\right)\sqrt[2009]{19^{2009}+5^{2009}}-\left(19^{2010}+5^{2010}\right)\)
\(=\left(19^{2009}.\sqrt[2009]{19^{2009}+5^{2009}}-19^{2010}\right)+\left(5^{2009}.\sqrt[2009]{19^{2009}+5^{2009}}-5^{2010}\right)\)
\(=19^{2009}\left(\sqrt[2009]{19^{2009}+5^{2009}}-19\right)+5^{2009}\left(\sqrt[2009]{19^{2009}+5^{2009}}-5\right)\)
\(>19^{2009}.\left(19-19\right)+5^{2009}.\left(5-5\right)=0\)
\(\Rightarrow\sqrt[2009]{A}>\sqrt[2009]{B}\)
\(\Rightarrow A>B\)
A= (\(\left(\frac{19^{2010}}{19}+\frac{5^{2010}}{5}\right)^{2010}\)=\(\frac{\left(5.19^{2010}+19.5^{2010}\right)^{2010}}{19^{2010}.5^{2010}}\)= A(1)/A(2)
B = \(\frac{\left(19^{2010}+5^{2010}\right)^{2010}}{19^{2010}+5^{2010}}\)= B(1)/B(2)
Ta thấy A(1) >B(1), A(2)<B(2) => A>B
ủa bạn duchinhle tại sao 19^2010.5^2010 lại lớn hơn 19^2020+5^2010
Vì 20009 x 2009 + 2008 < 2009 x 2009 + 2009
=>A < 1
Ta có: \(B=\frac{2009x2009+2009}{2008x2009+2010}=\frac{2009x\left(2008+1\right)+2009}{2008x2009+2010}=\frac{2008x2009+2009+2009}{2008x2009+2010}\)
\(B=\frac{2008x2009+4018}{2008x2009+2010}=\frac{2008x2009+2010+2008}{2008x2009+2010}=\frac{2008x2009+2010}{2008x2009+2010}+\frac{2008}{2008x2009+2010}\)
\(B=1+\frac{2008}{2008x2009+2010}>1\)
Mà A < 1
=>A < B
\(\frac{2008}{2009}=\frac{2009}{2009}-\frac{1}{2009}=1-\frac{1}{2009}\)
\(\frac{2009}{2010}=\frac{2010}{2010}-\frac{1}{2010}=1-\frac{1}{2010}\)
Vì 1/2009>1/2010=> 1-1/2009<1-1/2010
k nha
Ta có :
\(\frac{2008}{2009}=1-\frac{1}{2009}\)
\(\frac{2009}{2010}=1-\frac{1}{2010}\)
Do \(\frac{1}{2009}>\frac{1}{2010}\)
\(\Rightarrow1-\frac{1}{2009}< 1-\frac{1}{2010}\)
\(\Rightarrow\frac{2008}{2009}< \frac{2009}{2010}\)
Chúc bạn học tốt !!!
\(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+.....+\frac{1}{80}\)
\(=\left(\frac{1}{41}+\frac{1}{42}+\frac{1}{43}+\frac{1}{44}+.....+\frac{1}{60}\right)+\left(\frac{1}{61}+\frac{1}{62}+......+\frac{1}{80}\right)\)
\(>\left(\frac{1}{60}+\frac{1}{60}+\frac{1}{60}+.....+\frac{1}{60}\right)+\left(\frac{1}{80}+\frac{1}{80}+\frac{1}{80}+.....+\frac{1}{80}\right)\)
\(=\frac{1}{3}+\frac{1}{4}\)
\(=\frac{7}{12}\)
\(B=\frac{2008+2009+2010}{2009+2010+2011}=\frac{2008}{2009+2010+2011}+\frac{2009}{2009+2010+2011}+\frac{2010}{2009+2010+2011}\)
\(< \frac{2008}{2009}+\frac{2009}{2010}+\frac{2010}{2011}=A\)
Ta có:
\(\frac{2010}{2009}=\frac{2009+1}{2009}=1+\frac{1}{2009}\)
\(\frac{2011}{2010}=\frac{2010+1}{2010}=1+\frac{1}{2010}\)
Vì \(2009<2010=>\frac{1}{2009}>\frac{1}{2010}\)
=>\(\frac{2010}{2009}>\frac{2011}{2010}\)
Ai tích mình mình tích lại
Các bạn xem mình làm có đúng ko ?
\(\frac{2010}{2009}=\frac{2009+1}{2009}=\frac{2009}{2009}+\frac{1}{2009}=1+\frac{1}{2009}\)
\(\frac{2011}{2010}=\frac{2010+1}{2010}=\frac{2010}{2010}+\frac{1}{2010}=1+\frac{1}{2010}\)
Ta thấy : \(\frac{1}{2009}>\frac{1}{2010}\)=> \(1+\frac{1}{2009}>1+\frac{1}{2010}\)
Vậy ................................
de 1996xy chia het cho 5 thi y phai bang 0 hoac 5 . de 1996xy chia het cho 2 thi y phai bang 0.ta co 1996x0 chia het cho 9 khi x ={2 ,11,...} .do x la so co mot chu so nen x=2.vay so thoa man de bai la 199620
do 2009/2010<1,2010/2011<1,2011/2012<1,2012/2013<1suy ra 2009/2010+2010/2011+2011/2012+2012/2013<4