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\(\frac{2011}{2010}\times\frac{2012}{2011}\times\frac{2013}{2012}\times\frac{2014}{2013}\times\frac{1005}{1007}\)
\(=\frac{2014}{2010}\times\frac{1005}{1007}\)
\(=\frac{2\times1007\times1005}{2\times1005\times1007}\)
\(=1\)
$\frac{\frac{2010}{2011}}{\frac{2012}{2013}}+\frac{\frac{2011}{2012}}{\frac{2013}{2014}}+\frac{\frac{2012}{2013}}{\frac{2014}{2015}}$
$\frac{\frac{2010}{2011}}{\frac{2012}{2013}}+\frac{\frac{2011}{2012}}{\frac{2013}{2014}}+\frac{\frac{2012}{2013}}{\frac{2014}{2015}}$
$\frac{\frac{2010+2011+2012}{2011+2012+2013}}{\frac{2012+2013+2014}{2013+2014+2015}}$
$\frac{\frac{2010}{2011}+\frac{2011}{2012}+\frac{2012}{2013}}{\frac{2012+2013+2014}{2013+2014+2015}}$
$\frac{\frac{2010+2011+2012}{2011+2012+2013}}{\frac{2012}{2013}+\frac{2013}{2014}+\frac{2014}{2015}}$
ta có: \(\frac{2011-4022:\left(x-2009\right)}{2011\times2012\times2013}\)
\(M=\frac{2011-2\times2011:\left(x-2009\right)}{2011\times2012\times2013}\)
\(=\frac{2011\times\left(1-2:\left(x-2009\right)\right)}{2011\times2012\times2013}\)
\(=\frac{1-2:\left(x-2009\right)}{2012\times2013}\ge0\)
Để M có giá trị nhỏ nhất
\(\Rightarrow\frac{1-2:\left(x-2009\right)}{2012\times2013}=0\)
=> 1 - 2: (X-2009) = 0 : ( 2012 x 2013)
1-2:(X-2009) = 0
2: (X-2009) = 1
X-2009 = 2
X = 2 +2009
X=2011
KL: Giá trí nhỏ nhất của M là 0 tại X =2011
a) \(\frac{47}{32}>\frac{36}{46}\)Vì phân số \(\frac{47}{32}>1;\frac{36}{46}< 1\)nên \(\frac{47}{32}>\frac{36}{46}\)
b) \(\frac{199}{200}< \frac{200}{201}\)Vì \(\frac{199}{200}=\frac{199.201}{200.201};\frac{200}{201}=\frac{200.200}{201.200}\)
ta so sánh 199.201 và 200.200
199.201 = 199.(200+1) = 199.200+199
200.200 = 200.(199+1) = 200.199+200
Vì 199.200 + 199 < 200.199+200 nên \(\frac{199}{200}< \frac{200}{201}\)
c) \(\frac{2012.2010}{2011.2011}=\frac{\left(2011+1\right).2010}{2011.\left(2010+1\right)}=\frac{2011.2010+2010}{2011.2010+2011}\)
\(\frac{2013.2009}{2014.2008}=\frac{2013.\left(2008+1\right)}{\left(2013+1\right).2008}=\frac{2013.2008+2013}{2013.2008+2008}\)
ta so sánh : \(\frac{2010}{2011}< \frac{2013}{2008}\) vì \(\frac{2010}{2011}< 1;\frac{2013}{2008}>1\)
ta thấy 1=2010/2011+1/2011=2011/2012+1/2012 (1)
mà 1/2011>1/2012 nên để thõa mãn (1) thì 2010/2011<2011/2012.
Ta thấy: \(1-\frac{2010}{2011}=\frac{1}{2011}\)và \(1-\frac{2011}{2012}=\frac{1}{2012}\)
vÌ \(\frac{1}{2011}>\frac{1}{2012}\)
Vậy \(\frac{2010}{2011}< \frac{2011}{2012}\)