ln (3x) + ln (5X-2) = 3
更新1:
我讀..緊中6 math&stat. 唔該幫幫我!!
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回答 (2)
2007-01-11 7:19 pm
✔ 最佳答案
use the equality:ln(xy) = ln(x) + ln(y)
then:
ln(3x) + ln(5x-2) = 3
ln(3x*(5x-2)) = 3
3x*(5x-2) = e^3
by solving the above quadratic equation, we have:
x = 1.37 or x = -0.97
but you need to check that x should satisfy 3x > 0 and 5x-2 > 0
So, x = 1.37 (cor. to 2 d.p.)
2007-01-13 12:44 am
ln (3x) + ln (5x-2)=3
ln [3x(5x-2)]=ln (e^3)
ln (15x^2-6x)=ln (e^3)
15x^2-6x=e^3
15x^2-6x-e^3=0
x=[6士(36+60e^3)sqrt.]/30
ln [3x(5x-2)]=ln (e^3)
ln (15x^2-6x)=ln (e^3)
15x^2-6x=e^3
15x^2-6x-e^3=0
x=[6士(36+60e^3)sqrt.]/30
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https://hk.answers.yahoo.com/question/index?qid=20070111000051KK00826