`@` `\text {Ans}`

`\downarrow`

`315/380 = 1 - 65/380`

`316/380 = 1 - 65/381`

Mà `65/380 > 65/381`

`-> 1 - 65/380 < 1 - 65/381`

`-> 315/380 < 316/381`

`=> -315/380 > -316/381`

315/380=1-65/380

316/381=1-65/381

mà 65/380>65/381

nên 315/380<316/381

=>-315/380>-316/381

Ta có: \(-\frac{315}{380}=\frac{-380+65}{380}=-1+\frac{65}{380}\)

\(-\frac{316}{381}=\frac{-381+65}{381}=-1+\frac{65}{381}\)

mà \(\frac{65}{380}>\frac{65}{381}\) (380<381)

nên \(-\frac{315}{380}>-\frac{316}{381}\)

Ta có: \(-\frac{315}{380}=\frac{-380+65}{380}=-1+\frac{65}{380}\)

\(-\frac{316}{381}=\frac{-381+65}{381}=-1+\frac{65}{381}\)

mà \(\frac{65}{380}>\frac{65}{381}\) (380<381)

nên \(-\frac{315}{380}>-\frac{316}{381}\)

Câu 1 : 

\(\dfrac{-25}{37}\&\dfrac{-20}{31}\)

Ta thấy \(\dfrac{-25}{37}< \dfrac{-20}{37}\)

mà \(\dfrac{-20}{37}< \dfrac{-20}{31}\)

\(\Rightarrow\dfrac{-25}{37}< \dfrac{-20}{31}\)

Câu 2 :

\(\dfrac{2}{3}\&\dfrac{5}{7}\)

\(\dfrac{2}{3}:\dfrac{5}{7}=\dfrac{2}{3}.\dfrac{7}{5}=\dfrac{14}{15}< 1\)

Ta thấy \(\dfrac{8}{13}:\dfrac{5}{7}=\dfrac{8}{13}.\dfrac{7}{5}=\dfrac{56}{65}< 1\)

= nhau nha

\(2/3*4/5=8/15\)

\(4/5*2/3=8/15\)

\(=>2/3*4/5=4/5*2/3\) nhé

\(\dfrac{2004.2005-1}{2004.2005}=1-\dfrac{1}{2004.2005}\)

\(\dfrac{2005.2006-1}{2004.2006}=1-\dfrac{1}{2005.2006}\)

\(Vì\dfrac{1}{2004.2005}>\dfrac{1}{2005.2006}\Rightarrow1-\dfrac{1}{2004.2005}< 1-\dfrac{1}{2005.2006}\Rightarrow\dfrac{2004.2005-1}{2004.2005}< \dfrac{2005.2006-1}{2004.2006}\)

Mình cảm ơn

Lời giải:
a. $\frac{3}{-7}=\frac{-27}{63}$

$\frac{-5}{9}=\frac{-35}{63}$

Do $\frac{27}{63}< \frac{35}{63}$ nên $\frac{-27}{63}> \frac{-35}{63}$

$\Rightarrow \frac{3}{-7}> \frac{-5}{9}$

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b.

$-0,625=\frac{-625}{1000}=\frac{-5}{8}=\frac{-125}{200}$

$\frac{-19}{50}=\frac{-76}{200}> \frac{-125}{200}$

$\Rightarrow -0,625> \frac{-19}{50}$

c.

$-2\frac{5}{9}=-(2+\frac{5}{9})=\frac{-23}{9}=-(\frac{-23}{-9})$

-11>-78

nên \(-\dfrac{11}{3^7\cdot7^4}>-\dfrac{78}{3^7\cdot7^4}\)

<

=

>

5/15 < 12/8

5/15 = 3/9

5/15 > 5/8