16/15*17/16*18/17*...*2010/2009*2011*2010
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a,
\(\frac{45}{46}>\frac{2011}{2012}\)
b,
\(\frac{2010}{2011}< \frac{17}{16}\)
Hok tốt!
\(a,\frac{45}{46}\)và \(\frac{2011}{2012}\)
Ta có: \(1-\frac{45}{46}=\frac{1}{46};1-\frac{2011}{2012}=\frac{1}{2012}\)
\(\frac{1}{46}>\frac{1}{2012}\Rightarrow\frac{45}{46}>\frac{2011}{2012}\)
\(b,\frac{2010}{2011}\)và \(\frac{17}{16}\)
Ta có: \(\frac{2010}{2011}< 1;\frac{17}{16}>1\Rightarrow\frac{2010}{2011}< \frac{17}{16}\)
a) \(1=\frac{45}{46}+\frac{1}{46}\)
\(1=\frac{2011}{2012}+\frac{1}{2012}\)
Vì \(\frac{1}{46}>\frac{1}{2012}\)\(\Rightarrow\)\(\frac{45}{46}< \frac{2011}{2012}\)
b)Vì 2010/2011 < 1 và 17/16 > 1 => 2010/2011 < 17/16
\(=\frac{16}{15}\times\frac{17}{16}\times\frac{18}{17}\times...\times\frac{2010}{2009}\times\frac{2011}{2010}\)
\(=\frac{1}{15}\times2011\)
\(=\frac{2011}{15}\)
a)7/8 < 11/12
b) -2010/2011 > -2011/2012
c)-17/16 < -2/3
Dễ thấy:
\(\frac{2008}{2009}>\frac{2008}{2009+2010+2011}\)
\(\frac{2009}{2010}>\frac{2009}{2009+2010+2011}\)
\(\frac{2010}{2011}>\frac{2010}{2009+2010+2011}\)
=>\(\frac{2008}{2009}+\frac{2009}{2010}+\frac{2010}{2011}>\frac{2008}{2009+2010+2011}+\frac{2009}{2009+2010+2011}+\frac{2010}{2009+2010+2011}\)
Hay \(\frac{2008}{2009}+\frac{2009}{2010}+\frac{2010}{2011}>\frac{2008+2009+2010}{2009+2010+2011}\)
Vậy A > B
sửa lại : \(\frac{16}{15}\cdot\frac{17}{16}\cdot\frac{18}{17}\cdot...\cdot\frac{2010}{2009}\cdot\frac{2011}{2010}\)
\(=\frac{16\cdot17\cdot18\cdot...\cdot2010\cdot2011}{15\cdot16\cdot17\cdot...\cdot2009\cdot2010}\)
\(=\frac{2011}{15}\)