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2003/2004 + 2004/2005 + 2005/2003
= 1 - 1/2004 + 1 - 1/2005 + 1 + 1/2003 + 1/2003
=(1+1+1)-(1/2004 - 1/2003 + 1/2005 - 1/2003)
= 3 - (1/2004 - 1/2003 + 1/2005 - 1/2003)
Vì 1/2004 < 1/2003 ; 1/2005 < 1/2003
=>1/2004 - 1/2003 + 1/2005 - 1/2003 < 0
=> 3 - (...) > 3
Vậy. ...
K mình nha
\(\frac{2003}{2004}+\frac{2004}{2005}+\frac{2005}{2003}=1-\frac{1}{2004}+1-\frac{1}{2005}+1+\frac{2}{2003}\)
\(=3+\left(\frac{1}{2003}-\frac{1}{2004}\right)+\left(\frac{1}{2003}-\frac{1}{2005}\right)\)
Do \(\frac{1}{2003}>\frac{1}{2004}>\frac{1}{2005}.\) nên \(\left(\frac{1}{2003}-\frac{1}{2004}\right)+\left(\frac{1}{2003}-\frac{1}{2005}\right)>0\)
Vì vậy \(3+\left(\frac{1}{2003}-\frac{1}{2004}\right)+\left(\frac{1}{2003}-\frac{1}{2005}\right)>3\) (đpcm)
\(A=\frac{2003}{2004}+\frac{2004}{2005}+\frac{2005}{2003}\)
\(=(1-\frac{1}{2004})+(1-\frac{1}{2005})+(1+\frac{2}{2003})\)
\(=3+(\frac{1}{2003}+\frac{1}{2003}-\frac{1}{2004}-\frac{1}{2005})\)
Do\(\frac{1}{2003}\)>\(\frac{1}{2004}\)>\(\frac{1}{2005}\)
\(\Rightarrow\frac{1}{2003}+\frac{1}{2003}+\frac{1}{2004}+\frac{1}{2005}\)>\(0\)
\(\Rightarrow3+(\frac{1}{2003}-\frac{1}{2004}+\frac{1}{2003}-\frac{1}{2005})\)>\(3\)
\(\Rightarrow A\)>\(3\)
a) \(\frac{2005.2007-1}{2004+2005.2006}=\frac{\left(2014+1\right).2007-1}{2004+2005.2006}=\frac{2004+2005.2007-1}{2004+2005-2006}=\frac{2004+2005.2006}{2004+2005.2006}=1\)
\(A=\frac{2002}{2001}+\frac{2003}{2002}+\frac{2004}{2003}+\frac{2005}{2004}+\frac{2006}{2005}+\frac{2007}{2006}+\frac{2008}{2007}+\frac{2009}{2008}>\frac{2001}{2001}+\frac{2002}{2002}+\frac{2003}{2003}+\frac{2004}{2004}+\frac{2005}{2005}+\frac{2006}{2006}+\frac{2007}{2007}+\frac{2008}{2008}\)
\(A=\frac{2002}{2001}+\frac{2003}{2002}+\frac{2004}{2003}+\frac{2005}{2004}+\frac{2006}{2005}+\frac{2007}{2006}+\frac{2008}{2007}+\frac{2009}{2008}>1+1+1+1+1+1+1+1\)\(A=\frac{2002}{2001}+\frac{2003}{2002}+\frac{2004}{2003}+\frac{2005}{2004}+\frac{2006}{2005}+\frac{2007}{2006}+\frac{2008}{2007}+\frac{2009}{2008}>8\)
\(A>8\)
Bài làm:
Ta có: \(\frac{2004.2006-2003}{2005.2005-2004}\)
\(=\frac{\left(2005-1\right)\left(2005+1\right)-2003}{2005.2005-2004}\)
\(=\frac{2005.2005+2005-2005-1-2003}{2005.2005-2004}\)
\(=\frac{2005.2005-2004}{2005.2005-2004}\)
\(=1\)
\(\frac{2004.2006-2003}{2005.2005-2004}\)=\(\frac{2004.2005+2004-2003}{2005.2004+2005-2004}\)
=\(\frac{2004.2005+1}{2005.2004+1}\)
=1
Chúc bạn học tốt
1)2007/2006 > 1
2006/2008 < 1
2007/2006 > 1 > 2006/2008
2007/2006 >2006 /2008
2)1313/1414 = 1313: 101/1414 : 101 =13/14
13/14 = 13/14 => 1313/1414= 13/14
3) 97/96 - 1 = 1/96
96/95 - 1 = 1/95
1/96<1/95 => 97/96 < 96/95
4) 2007/2006 - 1 = 1/2006
2005/2004 - 1 = 1/2004
1/2006 < 1/2004 => 2007/2006 < 2005/2004
5) 2007/2006 - 1 = 1/2006
2008/2007 - 1 = 1/2007
1/2006 > 1/2007 => 2007/2006 > 2008/2007
1) so sánh với 1
2) rút gọn rồi so sánh
3,4,5 ) dùng phần bù ( phân số có phần bù lớn hơn thì phân số đó lớn hơn )