Solve 9^y + 5( 3^y - 10) = 0
Ans: [ 1.46 or 1.47 ]
求詳細部驟。THX!!
F.4 M1 Maths
2009-12-17 4:46 am
回答 (1)
2009-12-17 4:54 am
✔ 最佳答案
9^y + 5( 3^y - 10) = 0(3^2)^y + 5(3^y) - 50 = 0
(3^y)^2 + 5(3^y) - 50 = 0
Let 3^y be a :
a^2 + 5a - 50 = 0
(a - 5)(a +10) = 0
a = 5 or a = - 10
3^y = 5 or 3^y = - 10(rejected)
y log 3 = log 5
y = log 5 / log 3
2009-12-16 20:55:20 補充：
y = 1.464973521
y = 1.46(2 dec.)
參考: , 052
收錄日期: 2021-04-21 22:06:10
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20091216000051KK01408