一題F.4 MATHS

👨🏻‍🏫 學術台數學

Sesame

2013-06-29 5:25 am

if log25=x , log2=?
唔該俾埋步驟我 ><

回答 (3)

Tony

2013-06-29 5:39 am

✔ 最佳答案

log25=x
=> log(100/4)=x
=> log100 - log4=x
=> 2 - log(2^2)=x
=> 2 - 2log2=x
=> 2(1 - log2)=x
=> 1 - log2=x/2
=> log2=1 - (x/2)

參考: myself

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[匿名]

2013-06-29 7:23 pm

log25
=log[5^(2)]
=2log[5]
=2log[10/2]
=2log10-2log2
=2-2log2

Therefore,
log25=2-2log2
2log2=2-log25
log2=1-log25/2
log2=1-x/2

參考: me ^^

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風平浪靜海闊天空

2013-06-29 3:22 pm

log100=log(25*2*2)=log25+log2+log2
log100=log25+log2+log2
2=x+2log2
2log2=2-x
log2=1-(x/2)

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