# Help Needed Understanding Logs

• Oct 10th 2010, 03:29 PM
Help Needed Understanding Logs
I am requesting help understanding natural logs. I understand that if you have lets say

ln a = b

It can be rewritten as

a = e^b

What I would like to know is if there is any way I can simply a function with natural logs in it,

So if I had any function lets say

ln x = 10 - .5 ln A + .75 ln B - 1 ln C

Is there any way I could simplify that into normal terms without a long confusing jumble? If I had inputs, how do I go about solving a function like the above?

My understanding of natural logs is limited.

Thanks for any help.
• Oct 10th 2010, 03:35 PM
skeeter
go to the link and learn the laws of logarithms ... natural and otherwise.

Logarithms - Topics in precalculus
• Oct 10th 2010, 03:45 PM
Jhevon
Quote:

Originally Posted by bradm
I am requesting help understanding natural logs. I understand that if you have lets say

ln a = b

It can be rewritten as

a = e^b

What I would like to know is if there is any way I can simply a function with natural logs in it,

So if I had any function lets say

ln x = 10 - .5 ln A + .75 ln B - 1 ln C

Is there any way I could simplify that into normal terms without a long confusing jumble? If I had inputs, how do I go about solving a function like the above?

My understanding of natural logs is limited.

Thanks for any help.

Yes, you can simplify expressions like these using the laws of logarithms.

(i) $\displaystyle \dsiplaystyle \log_a b = c \implies a^c = b$

(ii) $\displaystyle \dsiplaystyle n \log_a X = \log_a (X^n)$

(iii) $\displaystyle \dsiplaystyle \log_a (XY) = \log_a X + \log_a Y$

(iv) $\displaystyle \dsiplaystyle \log_a \frac XY = \log_a X - \log_a Y$

(v) $\displaystyle \dsiplaystyle \log_a b = \frac {\log_c b}{\log_c a}$

Just a few of the rules that govern logs--the most important ones in my experience. Only some of these are needed to solve the problem you mentioned.