Question

So sánh -2/3 và 3/-4

Answer 1

có 

`(-2)/3=(-2xx4)/(3xx4)=(-8)/12`

`3/(-4)=(-3)/4=(-3xx3)/(4xx3)=(-9)/12`

vì `-8> -9`

`=>(-2)/3>3/(-4)`

Answer 2

Ta có:
\(-\dfrac{2}{3}=-\dfrac{8}{12}\)
\(-\dfrac{3}{4}=-\dfrac{9}{12}\)
Mà \(-\dfrac{8}{12}>-\dfrac{9}{12}\)
\(\Rightarrow-\dfrac{2}{3}>-\dfrac{3}{4}\)

Answer 3

Ta có : \(\dfrac{2}{3}=1-\dfrac{1}{3}\)

Mặt khác, \(\dfrac{3}{4}=1-\dfrac{1}{4}\)

Mà \(\dfrac{1}{4}< \dfrac{1}{3}\) \(\Rightarrow\)\(1-\dfrac{1}{4}>1-\dfrac{1}{3}\) Hay \(\dfrac{3}{4}>\dfrac{2}{3}\) \(\Rightarrow\) \(\dfrac{-2}{3}>\dfrac{3}{-4}\)

Vậy \(\dfrac{-2}{3}>\dfrac{3}{-4}\)