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Ta thấy
\(\dfrac{2010}{2011}< 1\)
\(\dfrac{2011}{2012}< 1\)
\(\dfrac{2012}{2013}< 1\)
\(\dfrac{2013}{2014}< 1\)
=> Tổng M của những phân số trên sẽ nhỏ hơn 1
=> M < 1
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\(a,\left(1-\dfrac{1}{10}\right)\times\left(1-\dfrac{1}{11}\right)\times\left(1-\dfrac{1}{12}\right)\times\left(1-\dfrac{1}{13}\right)\times\left(1-\dfrac{1}{14}\right)\times\left(1-\dfrac{1}{15}\right)=\dfrac{9}{10}\times\dfrac{10}{11}\times\dfrac{11}{12}\times\dfrac{12}{13}\times\dfrac{13}{14}\times\dfrac{14}{15}=\dfrac{9}{15}=\dfrac{3}{5}\)
\(b,\dfrac{2013\times2012-2}{2011+2011\times2013}=\dfrac{\left(2014-1\right)\times2012-2}{2011\times\left(2013+1\right)}=\dfrac{2014\times2012-2012-2}{2011\times2014}=\dfrac{2014\times2012-2014}{2011\times2014}=\dfrac{2014\times\left(2012-1\right)}{2011\times2014}=\dfrac{2011\times2014}{2011\times2014}=1\)
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<=> 1+\(\frac{1}{2014}\)+\(\frac{1}{x}\)=\(\frac{1}{x+1}\)+1+\(\frac{1}{2013}\)
<=> \(\frac{1}{2014}\)+\(\frac{1}{x}\)=\(\frac{1}{x+1}\)+\(\frac{1}{2013}\)
<=> \(\frac{1}{x}\)-\(\frac{1}{x+1}\)=\(\frac{1}{2013}\)-\(\frac{1}{2013+1}\) => x=2013
\(\frac{2015}{2014}+\frac{1}{x}=\frac{1}{x+1}+\frac{2014}{2013}\)
\(\Leftrightarrow\frac{2015}{2014}-1+\frac{1}{x}=\frac{1}{x+1}+\frac{2014}{2013}-1\)
\(\Leftrightarrow\frac{1}{2014}+\frac{1}{x}=\frac{1}{x+1}+\frac{1}{2013}\)
\(\Leftrightarrow\frac{x+2014}{2014x}=\frac{x+2014}{2013\left(x+1\right)}\)
\(\Leftrightarrow2014x=2013x+2013\)
\(\Leftrightarrow x=2013\)
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1).x:2+x:3=5/2
=>x.1/2+x.1/3=5/2
=>x(1/2+1/3)=5/2
=>x.5/6=5/2
=>x=5/2:5/6
=>x=3
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(1+1/2011)(1+1/2012)(1+1/2013)(1+1/2014)(1+1/2015) = 1.00248632521 NHỚ K NHA