I have the following

12.0*1.08^x =25.0

I need to find the value of x but Im lost on how its done.

Dave

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- May 20th 2012, 09:26 AMdavellew69finding the vaule of a raised power
I have the following

12.0*1.08^x =25.0

I need to find the value of x but Im lost on how its done.

Dave - May 20th 2012, 09:45 AMearbothRe: finding the vaule of a raised power
1. Divide through by 12.0.

2. Actually you have an exponential term at the LHS so transform the RHS into an exponential term with the same base:

$\displaystyle \displaystyle{1.08^x = 1.08^{\log_{1.08}\left(\frac{25}{12} \right)}}$ ............ So $\displaystyle x = \log_{1.08}\left(\frac{25}{12} \right)$

3. To get an approximate value for x use the base change formula:

$\displaystyle \log_a(b)=\frac{\ln(b)}{\ln(a)}$

Use your calculator. - May 20th 2012, 09:48 AMdavellew69Re: finding the vaule of a raised power
can this be done by using algebra?

- May 20th 2012, 12:14 PMKandersonRe: finding the vaule of a raised power
That is algebra.

- May 20th 2012, 01:55 PMbjhopperRe: finding the vaule of a raised power
I would simply use log base 10. No need to change.

log 12 + x(log 1.08) = log 25

x= 9.5 - May 20th 2012, 05:35 PMWilmerRe: finding the vaule of a raised power
1.08^x = 25/12

x = log(25/12) / log(1.08)

If a^x = b then x = log(b) / log(a) : tattoo that on your wrist!