So sánh các phân số sau 2009/2010 và 2010/2011

* Hướng dẫn giải

$a)Tacó:\frac{2009}{2010}+\frac{1}{2010}=\frac{2010}{2011}+\frac{1}{2011}=1$

$Mà \frac{1}{2010}>\frac{1}{2011} nên \frac{2009}{2010}<\frac{2010}{2011}$

$\begin{array}{l}b)Tacó:\frac{-199}{200}+\frac{-1}{200}=\frac{-200}{201}+\frac{-1}{201}=-1\\ \\ Mà \frac{-1}{200}<\frac{-1}{201} nên \frac{-199}{200}>\frac{-200}{201}\end{array}$

$\begin{array}{l}c)Tacó:\frac{103}{107}+\frac{4}{107}=\frac{113}{117}+\frac{4}{117}=1\\ \\ Mà \frac{4}{107}<\frac{4}{117} nên \frac{103}{107}<\frac{113}{117}\end{array}$

$\begin{array}{l}d)Tacó:\frac{-211}{137}+\frac{-63}{137}=\frac{-291}{177}+\frac{-63}{177}=-2\\ \\ Mà \frac{-63}{137}<\frac{-63}{177} nên \frac{-211}{137}>\frac{-291}{177}\end{array}$