A-maths~!

2008-08-01 7:14 am
1.若曲綫y=lnx的切綫垂直於直綫2x-2y+3=0,求切綫方程。

2.曲綫y=xe-1上哪一點的切綫平行於x軸?求這切綫方程。
1 ans:x+y+e-2=0
2 ans:(1,1/e) ,切綫方程y=1/e
更新1:

1.若曲綫y=xlnx的切綫垂直於直綫2x-2y+3=0,求切綫方程。

更新2:

2.曲綫y=xe^-x上哪一點的切綫平行於x軸?求這切綫方程。

回答 (2)

2008-08-03 11:17 pm
✔ 最佳答案
我還是覺得你的問題有錯!!!
因為答案根本是錯的!!!!!!

2008-08-03 15:17:49 補充:
Please refer to the following solution:

圖片參考:http://hk.geocities.com/stevieg_1023/E1.gif


圖片參考:http://hk.geocities.com/stevieg_1023/E2.gif
2008-08-01 4:12 pm
Slope of 2x - 2y +3 = 0 is 1.
Therefore, slope of required tangent is -1.
dy/dx = slope = 1/x = -1. That is x = -1. But x can never be negative for y=ln x !
So there is no such tangent.

2008-08-01 08:14:48 補充:
y = x/e is not a curve but a straight line.


收錄日期: 2021-04-23 20:36:40
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20080731000051KK03420

檢視 Wayback Machine 備份