數學正負分數的加減

(-7/4) - [(3/5) +(5/4)]

= (-35/20) - [(12/20) + (25/20)]

= (-35/20) - [(12 + 25)/20]

= (-35/20) - (37/20)

= (-35 - 37)/20

= -72/20

= -18/5

= -3又3/5

所給的答案錯誤。

2014-08-18 23:31:34 補充：
另解：

(-7/4) - [(3/5) + (5/4)]
= (-7/4) - (3/5) - (5/4)
= (-35/4) - (12/5) - (25/4)
= (-35 - 12 + 25)/20]
= -72/20
= -18/5
= -3又3/5 ...... 答案

2014-08-18 23:33:53 補充：
以上另解有一符號錯誤，應為：

(-7/4) - [(3/5) + (5/4)]
= (-7/4) - (3/5) - (5/4)
= (-35/4) - (12/5) - (25/4)
= (-35 - 12「-」 25)/20]
= -72/20
= -18/5
= -3又3/5 ...... 答案

2014-08-18 23:35:01 補充：
若要符合答案，題目改為：(-7/4) - [-(3/5) + (5/4)]

(-7/4) - [-(3/5) + (5/4)]
= (-7/4) + (3/5) - (5/4)
= (-35/4) + (12/5) - (25/4)
= (-35 + 12 - 25)/20]
= -48/20
= -12/5
= -2又2/5 ...... (答案)

ＴＯ：三號

是－３又５分之３才對

答：-3又3分之5

（計算過程如下）

圖片參考：https://s.yimg.com/lo/api/res/1.2/.LTMju18OBKEAxgRjuijGQ--/YXBwaWQ9dHdhbnN3ZXJzO3E9ODU-/http://i.imgur.com/wZMSCr4.png


2014-08-19 01:58:21 補充：
若題目為 -7/4-(-3/5+5/4) ，則解答如下


http://i.imgur.com/MwNwwsk.png

小黑的解答錯了
不然就是題目錯了
題目要改為-7/4-(-3/5+5/4)=??
解答才是負''二又五分之二''

-7/4-(3/5+5/4)
=-7/4-3/5-5/4
=-(7/4+3/5+5/4)