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Mathematics 20 Online
OpenStudy (rizags):

no

OpenStudy (jhannybean):

Cross multiply maybe?

jimthompson5910 (jim_thompson5910):

2 hints: a) \(\Large \frac{x^a}{x^b} = x^{a-b}\) b) see rule 2 on the link below http://www.purplemath.com/modules/logrules.htm

jimthompson5910 (jim_thompson5910):

good

jimthompson5910 (jim_thompson5910):

do you see how to isolate x from there?

jimthompson5910 (jim_thompson5910):

yep, log(a/b) is just a constant

jimthompson5910 (jim_thompson5910):

so basically raise both sides to the 1/[log(a/b)] power

jimthompson5910 (jim_thompson5910):

it's a bit ugly but it's still doable

jimthompson5910 (jim_thompson5910):

correct \[\LARGE x = \left(\frac{b}{a}\right)^{\frac{1}{\log\left(\frac{a}{b}\right)}}\] and that's as far as you can go in terms of simplifying it

jimthompson5910 (jim_thompson5910):

well I guess you could do this trick \[\LARGE x = \left(\frac{b}{a}\right)^{\frac{1}{\log\left(\frac{a}{b}\right)}}\] \[\LARGE x = \left(\left(\frac{a}{b}\right)^{-1}\right)^{\frac{1}{\log\left(\frac{a}{b}\right)}}\] \[\LARGE x = \left(q\right)^{-\frac{1}{\log\left(q\right)}} \ ... \ \text{Let } q = \frac{a}{b}\] but that's all I can think of in terms of simplification (it's not much of a simplification really)

jimthompson5910 (jim_thompson5910):

you're welcome

jimthompson5910 (jim_thompson5910):

how exactly?

jimthompson5910 (jim_thompson5910):

Oh I see, we can use the change of base formula \[\LARGE x = \left(q\right)^{-\frac{1}{\log\left(q\right)}}\] \[\LARGE x = \left(q\right)^{-\frac{1}{\log_{10}\left(q\right)}}\] \[\LARGE x = \left(q\right)^{-\frac{1}{\log\left(q\right)/\log(10)}}\] \[\LARGE x = \left(q\right)^{-\frac{\log(10)}{\log\left(q\right)}}\] \[\LARGE x = \left(q\right)^{-\log_q(10)}\] \[\LARGE x = \left(q\right)^{\log_q(10^{-1})}\] \[\LARGE x = 10^{-1}\] \[\LARGE x = \frac{1}{10}\]

jimthompson5910 (jim_thompson5910):

So you can have the shortcut rule \[\LARGE \frac{1}{\log_{x}(y)} = \log_{y}(x)\]

jimthompson5910 (jim_thompson5910):

you're welcome

OpenStudy (jhannybean):

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