solve:
(a) ln(x^2+5x) = 2ln(x+1)
(b) log(7x-12) = 2logx
兩題log數唔識做
2012-04-23 6:12 pm
回答 (2)
2012-04-23 6:40 pm
✔ 最佳答案
a) ln (x2 + 5x) = 2 ln (x + 1)ln (x2 + 5x) = ln (x + 1)2
x2 + 5x = (x + 1)2
x2 + 5x = x2 + 2x + 1
3x = 1
x = 1/3
b) log (7x - 12) = 2 log x
log (7x - 12) = log x2
7x - 12 = x2
x2 - 7x + 12 = 0
(x - 4)(x - 3) = 0
x = 4 or 3
參考: 原創答案
收錄日期: 2021-04-28 14:40:37
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20120423000051KK00154