F.4 Maths
回答 (1)
2010-05-06 6:22 am
✔ 最佳答案
2e^2x -5e^-2x =3Let y be e^2x :
then e^-2x = (e^2x)^-1 = 1 / (e^2x) = 1/y
The equations becomes
2y - 5/y = 3
2y^2 - 5 = 3y
2y^2 - 3y - 5 = 0
(2y - 5)(y + 1) = 0
y = e^2x = 5/2
In (e^2x) = In (5/2)
2x In e = In (5/2)
2x = In(5/2)
x = (1/2)In(5/2) = 0.46(2dec.places)
or y = e^2x = - 1 (rejected)
收錄日期: 2021-04-21 22:11:43
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100505000051KK01646