# Solving an Exponetial & Log Equation.

• Apr 20th 2008, 09:00 AM
Itsbaxagain
Solving an Exponetial & Log Equation.
Okay, so here is what I have $P=1045ln(0.0016f+1)$

P= perceived pitch (mels), F= frequency (hertz)

I need to solve when P= 1500 algebraically.

Can anyone give me some sparks to start my engine? Thanks.
• Apr 20th 2008, 09:04 AM
Moo
Hello,

Well, divide each side of the equation by 1045, then take the exponential of the two sides, and ...
• Apr 20th 2008, 09:18 AM
Itsbaxagain
Quote:

Originally Posted by Moo
Hello,

Well, divide each side of the equation by 1045, then take the exponential of the two sides, and ...

Well after doing that and reducing I got: $\frac{300}{209}=ln(.0016f+1)$ I don't know how to break up the ln part. Do I need it in log for like $\frac{300}{209}=\frac{log(.0016f+1)}{log(e)}$ but still I don't know how to break apart the $log(.0016f+1)$
• Apr 20th 2008, 09:21 AM
Moo
If ln is the neperian one :

$\ln(0.016f+1)=300/209 \Longleftrightarrow 0.016f+1=e^{300/209}$

If it's the logarithm in basis 10 :

$\ln(0.016f+1)=300/209 \Longleftrightarrow 0.016f+1=10^{300/209}$
• Apr 20th 2008, 09:32 AM
Itsbaxagain
I confused, I can't see how I get the answer because when I find the answer using my calculator I get approx:1278.84
• Apr 20th 2008, 09:34 AM
Moo
I should have added "then, isolate f " (Thinking)
• Apr 20th 2008, 09:49 AM
Itsbaxagain
Quote:

Originally Posted by Moo
I should have added "then, isolate f " (Thinking)

I am trying to think but I just can't figure it out.