giúp mình so sánh phân số:2006/2005 và 2007/2006
giúp mình liền nha
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a)2012/2013<2013/2014
b)2003x........< 2007x......
cho mình nha
giải
ta thấy 1 = 2004/2005 + 1/2005
1= 2005/2006 + 1/ 2006
vì 1/ 2005 > 1/2006 ( phần bù )
nên suy ra : 2004 / 2005 < 2005 /2006
Ta có: \(A=\dfrac{2005}{2006}+\dfrac{2006}{2007}+\dfrac{2007}{2005}=\dfrac{2006-1}{2006}+\dfrac{2007-1}{2007}+\dfrac{2005}{2005}+\dfrac{1}{2005}+\dfrac{1}{2005}\)\(=1+1+1+\left(\dfrac{1}{2005}-\dfrac{1}{2006}+\dfrac{1}{2005}-\dfrac{1}{2007}\right)\)
\(=3+\left(\dfrac{1}{2005}-\dfrac{1}{2006}+\dfrac{1}{2005}-\dfrac{1}{2007}\right)\)
Ta thấy: \(\dfrac{1}{2005}>\dfrac{1}{2006};\dfrac{1}{2005}>\dfrac{1}{2007}\) \(\Rightarrow\dfrac{1}{2005}-\dfrac{1}{2006}+\dfrac{1}{2005}-\dfrac{1}{2007}>0\)
\(\Rightarrow A>3\)
Ta có: \(\frac{2005}{2006}=1-\frac{1}{2006}\); \(\frac{2006}{2007}=1-\frac{1}{2007}\)
Vì \(\frac{1}{2006}>\frac{1}{2007}\) nên \(1-\frac{1}{2006}
Ta có: 20052006 =1−12006 ; 20062007 =1−12007
Vì 12006 >12007 nên 1−12006 <1−12007
Vậy
ta có:\(1-\frac{2005}{2006}=\frac{1}{2006}\)
\(1-\frac{2006}{2007}=\frac{1}{2007}\)
vì 2006<2007
=>\(\frac{1}{2006}>\frac{1}{2007}\)
=>\(\frac{2005}{2006}>\frac{2006}{2007}\)
a) Ta có:
\(1-\frac{2005}{2006}=\frac{1}{2006}\)
\(1-\frac{2006}{2007}=\frac{1}{2007}\)
Vì \(\frac{1}{2006}>\frac{1}{2007}\)nên \(\frac{2005}{2006}>\frac{2006}{2007}\)
b) Ta có:
\(\frac{2008}{2007}-1=\frac{1}{2007}\)
\(\frac{2007}{2006}-1=\frac{1}{2006}\)
Vì \(\frac{1}{2006}>\frac{1}{2007}\)nên \(\frac{2008}{2007}< \frac{2007}{2006}\)
a, \(\frac{2005}{2006}v\text{à}\frac{2006}{2007}\)= \(\frac{2005\cdot2007}{2006\cdot2007}\)và \(\frac{2006\cdot2006}{2007\cdot2006}\)
= \(\frac{4024035}{4026042}\)< \(\frac{4024036}{4026042}\)
b, \(\frac{2008}{2007}v\text{à}\frac{2007}{2006}\)= \(\frac{2008\cdot2006}{2007\cdot2006}v\text{à}\frac{2007\cdot2007}{2006\cdot2007}\)
=\(\frac{4028048}{4026042}\)< \(\frac{4028049}{4026042}\)
ta có:
2006/2005 - 1 = 1/2005
2007/2006 - 1 = 1/2006
=>1/2005 > 1/2006 => 2006/2005 > 2007/2006