1. solve th following equation
logx/log3+log9/logx=3
Logarithmic
2012-09-04 4:39 am
回答 (3)
2012-09-04 6:22 pm
✔ 最佳答案
Let u=log x/log 3, therefore(log x/log 3) + (log 9/log x) = 3
(log x/log 3) + (2log 3/log x) =3
u + 2/u = 3
u^2 - 3u + 2 = 0
(u - 1)(u - 2) = 0
u = 1 or 2
log x/log 3 = 1 or 2
log x = log 3 or 2log 3
log x = log 3 or log 9
x = 3 or 9 (ans.)
2012-09-05 21:11:09 補充：
希望 Wai Ching 唔好俾老師捉倒。出來做嘢唔好俾差人拉。
2012-09-06 2:21 am
Let u=log x/log 3,
(log x/log 3) + (log 9/log x) = 3
(log x/log 3) + (2log 3/log x) =3
u + 2/u = 3
u^2 - 3u + 2 = 0
(u - 1)(u - 2) = 0
u = 1 or 2
log x/log 3 = 1 or 2
log x = log 3 or 2log 3
log x = log 3 or log 9
x = 3 or 9
(log x/log 3) + (log 9/log x) = 3
(log x/log 3) + (2log 3/log x) =3
u + 2/u = 3
u^2 - 3u + 2 = 0
(u - 1)(u - 2) = 0
u = 1 or 2
log x/log 3 = 1 or 2
log x = log 3 or 2log 3
log x = log 3 or log 9
x = 3 or 9
參考: me
2012-09-04 4:49 am
參考: My Maths World
收錄日期: 2021-04-13 18:57:44
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120903000051KK00679