Re: [中學] 對數問題
(log x + log 2)(log x + log 3) = 1
2
(log x) + (log 2 + log 3)log x + (log 2)(log 3) - 1 = 0
2
令 log x = t 、 原式 => t + (log 6)t + (log 2)(log 3) - 1 = 0
得 t 的兩根 t1 = log a 、 t2 = log b
由根與係數關係
t1 + t2 = -log 6 = log a + log b
1
log (ab) = log ---
6
1
所以 ab = ---
6
: http://i.imgur.com/zsYyJvE.jpg
3 2 (-3/2)
a b = 1 => b = a
3
所以 log b = - ---
a 2
/ 2 3\ 5
log | a b | = 2 + 3log b = - ---
a\ / 2
: 請問各位～這兩題的對數題目要如何解呢謝謝～
--
※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 1.169.251.167
※ 文章網址: https://www.ptt.cc/bbs/Math/M.1481878138.A.025.html
※ 編輯: freePrester (1.169.251.167), 12/16/2016 16:50:41
推
12/16 18:54, , 1F
12/16 18:54, 1F
討論串 (同標題文章)
