負分數的乘法運算

兩同號分數相乘：乘積為正。

例 $(-3)\times (-\dfrac27)=3\times \dfrac27=\dfrac{3\times 2}{7}=\dfrac67$

$(-\dfrac23)\times (-\dfrac45)=\dfrac23\times \dfrac45=\dfrac{2\times 4}{3\times 5}=\dfrac{8}{15}$

兩異號分數相乘：乘積為負。

例 $\dfrac{33}{14}\times (-\dfrac{21}{22})=-(\dfrac{33}{14}\times \dfrac{21}{22})=-(\dfrac{3\times 3}{2\times 2})=-\dfrac94$

$(-\dfrac45)\times 6\dfrac14=-(\dfrac45\times \dfrac{25}{4})=-(\dfrac{1\times 5}{1\times 1})=-\dfrac51=-5$

觀念影片