e^x + e^(-x) = 3 ,x =?
因為諗左好耐都唔識計
希望有人可以step by step 咁講點計
e^x + e^(-x) = 3 ,x =?
2010-02-23 1:47 am
回答 (1)
2010-02-23 2:06 am
✔ 最佳答案
e^x + e^(-x) = 3設 e^x = y
則e^(-x) = 1/(e^x) = 1/y
y + 1/y = 3
y^2 + 1 = 3y
y^2 - 3y + 1 = 0
y = [3 +/- √(9 - 4)]/2
y = (3 + √5)/2 or (3 - √5)/2
e^x = (3 + √5)/2 or (3 - √5)/2
x = In (3 + √5)/2 or In (3 - √5)/2
x = 0.9624 or -0.9624
收錄日期: 2021-04-21 22:10:09
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20100222000051KK01085