Logarithms 兩題

L.K.

1.)log(x²+4)-2logx=1
find x

2.)log(x²+4)-log(x²)=1
find x

小莓。改

1)
log(x^2+4) - 2log x =1
x^2+4 = 10x^2
x = 2/3

2)
similarly,
x = 2/3 or -2/3 [since of syllabus of CE didn't define the field gone when log(-1)]

-終場ソ使者-

log(x²+4) - 2log x =1
log((x²+4)/x²)=log10
((x²+4)/x²)=10
x²+4=10x²
(3x)²-2²=0
(3x-2)(3x+2)=0
x=2/3  or  x=-2/3

2) is the same

L.K.

[[onion_56]] 咁姐係點..
正確D黎講.
X會唔會=-2/3

小山田萬太

4# L.K.

1)
log(x^2+4) - 2log x =1
x^2+4 = 10x^2
x = 2/3

2)
similarly,
x = 2/3 or -2/3 [since of syllabus of CE didn't define the field gone when log(-1)]
小莓。改 發表於 11-11-2008 13:33

樓主試下用部將log -2/3 輸入去計數機 睇下會點
如果照小莓。改既意思 CE以上程度  可以log -2/3?

[S]【YU】

應該可以 -2/3 , 因為可以square入去.