x-1/x+1 - x+1/x-1
= (x-1)(x-1)/(x+1)(x-1) - (x+1)(x+1)/(x+1)(x-1)
最想知跟住點變成咁
= x^2-x-x+1 - x^2-x-x-1 <<重點/(x+1)(x-1)
= -4x/(x+1)(x-1)
個重點果到佢係咪用左cross method先計到
p.s條數係中2的
中2果陣我幾乎係訓堂so唔明
關於數學一條數
2007-09-10 4:21 am
回答 (1)
2007-09-10 4:31 am
✔ 最佳答案
你寫錯step！唔係 (x-1)(x-1)/(x+1)(x-1) - (x+1)(x+1)/(x+1)(x-1)
應該係： [(x-1)(x-1) - (x+1)(x+1)]/(x+1)(x-1)
分子：
(x-1)(x-1)乘出黎=x^2-x-x+1
(x+1)(x+1)乘出黎=x^2+x+x+1
所以，分子=(x^2-x-x+1)-(x^2+x+x+1)=x^2-x-x+1-x^2-x-x-1=-4x
所以，答案係-4x/(x+1)(x-1)
收錄日期: 2021-04-30 20:50:05
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070909000051KK04536