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\(\frac{2008\cdot2009+4018}{2010\cdot2011-4020}=\frac{2008\cdot2009+2009\cdot2}{2010\cdot2011-2010\cdot2}=\frac{\left(2008+2\right)\cdot2009}{2010\left(2011-2\right)}=\frac{2010\cdot2009}{2010\cdot2009}=1\)
b
2008.2009 + 4018 = 2008.2009 + 2.2009 0.25
= 2009.(2008+2) = 2009.2010 0.25
2010.2011-4020 = 2010.2011-2.2010 0.25
= 2010.(2011-2) = 2010.2009 0.25
⇒2008.2009 4018
2010.2011 4020
+
−
= 1
Ta co:\(\frac{2008.2009+4018}{2010.2011-4020}=\frac{2008.\left(2011-2\right)+4018}{\left(2008+2\right).2011-4020}\)
\(=\frac{2008.2011-2008.2+4018}{2008.2011+2011.2-4020}=\frac{2008.2011+4018-4016}{2008.2011+4022-4020}\)
\(=\frac{2008.2011+2}{2008.2011+2}=1\)
Bài làm :
Ta có :
\(A=\frac{2008.2009+4018}{2010.2011-4020}\)
\(A=\frac{2008.2009+2009.2}{2010.2011-2010.2}\)
\(A=\frac{2009.\left(2008+2\right)}{2010.\left(2011-2\right)}\)
\(A=\frac{2009.2010}{2010.2009}=1\)
Vậy A=1 .
Chúc bạn học tốt !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
\(A=\frac{2008.2009+4018}{2010.2011-4020}\)
\(A=\frac{2008.2009+2009.2}{2010.2011-2010.2}\)
\(A=\frac{2009.\left(2008+2\right)}{2010.\left(2011-2\right)}\)
\(A=\frac{2009.2010}{2010.2009}=1\)
Vậy ....
Ta có :
\(B=\frac{2008+2009+2010}{2009+2010+2011}=\frac{2008}{2009+2010+2011}+\frac{2009}{2009+2010+2011}+\frac{2010}{2009+2010+2011}\)
Vì :
\(\frac{2008}{2009}>\frac{2008}{2009+2010+2011}\)
\(\frac{2009}{2010}>\frac{2009}{2009+2010+2011}\)
\(\frac{2010}{2011}>\frac{2010}{2009+2010+2011}\)
Nên \(\frac{2008}{2009}+\frac{2009}{2010}+\frac{2010}{2011}>\frac{2008}{2009+2010+2011}+\frac{2009}{2009+2010+2011}+\frac{2010}{2009+2010+2011}\)
\(\Rightarrow\)\(A>B\)
Vậy \(A>B\)
Ta có: \(B=\frac{2008+2009+2010}{2009+2010+2011}\)
\(=\frac{2008}{2009+2010+2011}+\frac{2009}{2009+2010+2011}+\frac{2010}{2009+2010+2011}\)
Vì \(\frac{2008}{2009}>\frac{2008}{2009+2010+2011}\)
\(\frac{2009}{2010}>\frac{2009}{2009+2010+2011}\)
\(\frac{2010}{2011}>\frac{2010}{2009+2010+2011}\)
nên \(\frac{2008}{2009}+\frac{2009}{2010}+\frac{2010}{2011}>\frac{2008+2009+2010}{2009+2010+2011}\)
hay A > B
Vậy A > B
\(B=\dfrac{2008+2009+2010}{2009+2010+2011}=\dfrac{2008}{2009+2010+2011}+\dfrac{2009}{2009+2010+2011}+\dfrac{2010}{2009+2010+2011}\)Ta có : \(\dfrac{2008}{2009}>\dfrac{2008}{2009+2010+2011}\)
\(\dfrac{2009}{2010}>\dfrac{2009}{2009+2010+2011}\)
\(\dfrac{2010}{2011}>\dfrac{2010}{2009+2010+2011}\)\(=>\dfrac{2008}{2009}+\dfrac{2009}{2010}+\dfrac{2010}{2011}>\dfrac{2008+2009+2010}{2009+2010+2011}\)
Hay A > B
ta thấy:
\(\dfrac{2008}{2009}>\dfrac{2008}{2009+2010}\)(1)
\(\dfrac{2009}{2010}>\dfrac{2009}{2009+2010}\)(2)
từ 1 và 2 cộng vế với vế ta dc \(\dfrac{2008}{2009}+\dfrac{2009}{2010}>\dfrac{2008}{2009+2010}+\dfrac{2009}{2009+2010}=\dfrac{2008+2009}{2009+2010}\)
chúc bạn học tốt ^^
Ta có :\(\dfrac{2008.2009+4018}{2010.2011-4020}=\dfrac{2008.2009+2009.2}{2010.2011-2010.2}\)
\(=\dfrac{2009.\left(2008+2\right)}{2010\left(2011-2\right)}=\dfrac{2009.2010}{2010.2009}=1\)