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View Full Version : Logarithms... it really confuses me!


yamna
Dec 16, 2006, 04:01 PM
OK so this time I am really trying to solve themm but I don't know how to.. I have couple of solutions but I don't think eighter of them is right:

25^x=18
log 25^x=log 18
xlog25= log 18
x=log 18/log 25
x=log 18-25
x=log (-7)

but actually I am not supposed to solve it.. I am just suppose to convert it to expnential if its in lorigmathic form... and its in lorigmathic form I have to convert it to expoenential...

is it suppose to be like:

log(base 25) 18= x??

2. log(base 2)128
so I have no idea how to solve itt.. I tried it with the change base formula but its not working that wayyyy...

waiting for some replies.. thanxxx

Capuchin
Dec 16, 2006, 05:03 PM
For your first question, can you not just use the base change formula to get the correct answer? You seem to be doing everything else right.

I think the second one is trying to get you to understand what logarithm actually is. You should be able to work it out in your head if you understand it well enough! :)

If you need more help just let me know! :)

yamna
Dec 16, 2006, 05:49 PM
[QUOTE=yamna]OK so this time I am really trying to solve themm but I don't know how to.. I have couple of solutions but I don't think eighter of them is right:

25^x=18
log 25^x=log 18
xlog25= log 18
x=log 18/log 25
x=log 18-25
x=log (-7)

but actually I am not supposed to solve it.. I am just suppose to convert it to expnential if its in lorigmathic form... and its in lorigmathic form I have to convert it to expoenential...

is it suppose to be like:

log(base 25) 18= x??

2. log(base 2)128
so I have no idea how to solve itt.. I tried it with the change base formula but its not working that wayyyy...



THANXX... I HAVE GOT THE ASNWER... I CHATTTED WITH THIS GUY (Capuchin)ON MSN.. AND HE GAVE ME ALL THE DIRECTIONS AND HOW TO APPROCH MY ANSWER :

so it's 25^x = 18
log(25) both sides
so log(25)25^x = log(25)18
log(25)25^x = x
so you can simplify that
and you get what you stated
log(25)18 = x


log(base 2)128
learn to read that question as "what power to i have to raise 2 to to get 128?"
2^x = 128
2, 4, 8, 16, 32, 64, 128
so it's 7

(Edited by Capuchin for clarity)

asterisk_man
Dec 16, 2006, 07:04 PM
Just wanted to congratulate yamma on doing the right thing for the community. Namely, post the final result here even though you determined it elsewhere. I think many people underestimate the number of others who can use this site as a resource of previously answered questions.

Also good work on learning!

Capuchin
Dec 16, 2006, 07:07 PM
*cough* I asked him to *cough*

Capuchin++

It's pretty much copy pasted out of the chat too... but I think he understood it.. nice kid :)