Vì \(2012\times2013< 2012\times2013+1\)và \(2013>2012\)

\(\Rightarrow\)\(\frac{2012\times2013}{2012\times2013+1}< 1< \frac{2013}{2012}\)

\(\Rightarrow\)\(\frac{2012\times2013}{2012\times2013+1}< \frac{2013}{2012}\)

\(\Rightarrow\)\(A< B\)

Vậy \(A< B\)

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ta có : \(\frac{2012\times2013}{2012\times2013}\)có giá trị = 1.nên A có giá trị bằng 2

ta thấy : B = 1,000497018 => A > B

nhớ k nhá

A=4052170

B=1/1/2012

\(=1+\dfrac{1}{2012}-1-\dfrac{1}{2013}-\dfrac{1}{2012}+\dfrac{1}{2013}=0\)

= 0

\(\dfrac{1}{4050156}\) - \(\dfrac{1}{2012x2013}\)

=

Ta có \(\frac{2012.2013}{2012.2013+1}\)và \(\frac{2013}{2012}\)

Vì \(\frac{2012.2013}{2012.2013+1}< 1< \frac{2013}{2012}\)

nên \(\frac{2012.2013}{2012.2013+1}< \frac{2013}{2012}\)

\(\frac{2012}{2013}\)và \(\frac{2011}{2012}\)

phàn bù của \(\frac{2012}{2013}\)là \(\frac{1}{2013}\)

phàn bù của \(\frac{2011}{2012}\)là \(\frac{1}{2012}\)

Vì \(\frac{1}{2012}>\frac{1}{2013}\Rightarrow\frac{2012}{2013}>\frac{2011}{2012}\)

Ta có : \(\frac{2012\cdot2013}{2012\cdot2013+1}< 1\)

             \(\frac{2013}{2012}>1\)

\(\Rightarrow\frac{2012\cdot2013}{2012\cdot2013+1}< \frac{2013}{2012}\)

Có : \(\frac{2012}{2013}=1-\frac{2012}{2013}=\frac{2013}{2013}-\frac{2012}{2013}=\frac{1}{2013}\)

         \(\frac{2011}{2012}=1-\frac{2011}{2012}=\frac{2012}{2012}-\frac{2011}{2012}=\frac{1}{2012}\)

Vì \(2013< 2012\)nên \(\frac{1}{2013}< \frac{1}{2012}\)hay \(\frac{2012}{2013}< \frac{2011}{2012}\)

So sánh các phân số sau :

\(\frac{2012\times2013}{2012\times2013+1}\)và \(\frac{2013}{2012}\)

Ta có : 

\(\frac{2012\times2013}{2012\times2013+1}\)

\(=\frac{1}{1}=1\)( cùng rút gọn 2012 x 2013 )

Vì \(1< \frac{2013}{2012}\)nên \(\frac{2012\times2013}{2012\times2013+1}< \frac{2013}{2013}\).

\(\frac{2012}{2013}\)và \(\frac{2011}{2012}\)

Ta có : 

\(1-\frac{2012}{2013}=\frac{1}{2013};1-\frac{2011}{2012}=\frac{1}{2012}\)

Vì \(\frac{1}{2013}< \frac{1}{2012}\)nên \(\frac{2012}{2013}< \frac{2011}{2012}\)

~ Chúc  bạn hok tốt ~

Ta có:

\(\frac{2011}{2012}=1-\frac{1}{2012}\)

\(\frac{2012}{2013}=1-\frac{1}{2013}\)

\(\frac{2013}{2014}=1-\frac{1}{2014}\)

Do \(\frac{1}{2012}>\frac{1}{2013}>\frac{1}{2014}\)=> \(-\frac{1}{2012}< -\frac{1}{2013}< -\frac{1}{2014}\)

=> \(1-\frac{1}{2012}< 1-\frac{1}{2013}< 1-\frac{1}{2014}\)

=> \(\frac{2011}{2012}< \frac{2012}{2013}< \frac{2013}{2014}\)

1.

\(A=\frac{1.2}{2.2}.\frac{2.3}{3.3}.\frac{3.4}{4.4}......\frac{2012.2013}{2013.2013}\)

\(A=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}.........\frac{2012}{2013}\)

\(A=\frac{1.2.3.4.....2012}{2.3.4.5......2013}\)

\(A=\frac{1}{2013}\)

\(B=\frac{2012.2013-2012.2012}{2012.2011+2012.2}\)

\(B=\frac{2012\left(2013-2012\right)}{2012\left(2011+2\right)}\)

\(B=\frac{2013-2012}{2011+2}\)

\(B=\frac{1}{2013}\)

\(Vì:\frac{ 1}{2013}=\frac{1}{2013}\)

\(\Rightarrow\frac{1.2}{2.2}.\frac{2.3}{3.3}.\frac{3.4}{4.4}......\frac{2012.2013}{2013.2013}=\frac{2012.2013-2012.2012}{2012.2011+2012.2}\)

\(Hay: A=B\)

\(A=\frac{1\times2}{2\times2}\times\frac{2\times3}{3\times3}\times\frac{3\times4}{4\times4}\times\frac{4\times5}{5\times5}\times...\times\frac{2012\times2013}{2013\times2013}\)

\(\Rightarrow A=\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times...\times\frac{2012}{2013}\)

\(\Rightarrow A=\frac{1\times2\times3\times4\times...\times2012}{2\times3\times4\times5\times...\times2013}\)

\(\Rightarrow A=\frac{1}{2013}\)

\(B=\frac{2012\times2013-2012\times2012}{2012\times2011+2012\times2}\)

\(\Rightarrow B=\frac{2012\times\left(2013-2012\right)}{2012\times\left(2011+2\right)}\)

\(\Rightarrow B=\frac{2012\times1}{2012\times2013}\)

\(\Rightarrow B=\frac{1}{2013}\)

Ta có : 

\(\frac{1}{2013}M=\frac{2013^{2012}+2012}{2013^{2012}+2013}=\frac{2013^{2012}+2013}{2013^{2012}+2013}-\frac{1}{2013^{2012}+2013}=1-\frac{1}{2013^{2012}+2013}\)

Lại có : 

\(\frac{1}{2013}N=\frac{2013^{2011}+2012}{2013^{2011}+2013}=\frac{2013^{2011}+2013}{2013^{2011}+2013}-\frac{1}{2013^{2011}+2013}=1-\frac{1}{2013^{2011}+2013}\)

Vì \(\frac{1}{2013^{2012}+2013}< \frac{1}{2013^{2011}+2013}\) nên \(M=1-\frac{1}{2013^{2012}}>N=1-\frac{1}{2013^{2011}+2013}\)

Vậy \(M>N\)

Chúc bạn học tốt ~ 

A=B vì( a=1/2013 ; b=1/2013)