HOW TO SIMPLY (log a/b)^2 + 4logalogb - (logab)^2

2007-03-10 2:28 am
HOW TO SIMPLY (log a/b)^2 + 4logalogb - (logab)^2
要步驟和答案, thx~

回答 (4)

2007-03-10 2:37 am
✔ 最佳答案
(log a/b)^2 + 4logalogb - (logab)^2
= (log a-logb)^2 + 4logalogb - (loga+logb)^2
= (log a)^2 - 2logalogb +(log b)^2 +4logalogb - ((log a)^2 + 2logalogb +(log b)^2)
= (log a)^2 - 2logalogb +(log b)^2 +4logalogb - (log a)^2 - 2logalogb -(log b)^2
= 0
2007-03-10 3:26 am
(log a/b)^2 + 4logalogb - (logab)^2
=(log a-log b)^2-(log a+log b)^2+4log a log b
=(2log a)(-2log b)+4log a log b<-----------a^2-b^2=(a+b)(a-b)
=-4log a log b+4log a log b
=0
2007-03-10 2:39 am
Here is the solution:

圖片參考:http://xs413.xs.to/xs413/07105/ggdgdgrgrg.png
2007-03-10 2:36 am
(log a/b)^2 + 4logalogb - (logab)^2
= (log a - log b)^2 + 4 logalogb - (log a + log b)^2
>>>log a/b = log a - log b and logab = log a + log b

= (log a)^2 - 2logalogb + (log b)^2 + 4 logalogb - (log a)^2 - 2 logalogb - (log b)^2
>>>乘開 (log a - log b)^2 同埋 (log a + log b)^2

= 0


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