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estefania · Jan 27, 2009, 09:18 AM

expand:
log base 7 a/5

condense:
g log 7

solve:
log base 7 5=1/3log base 7 (x-1)

approximate using the change of base formula (to two decimal places):
log base 3 13=?

ebaines · Jan 27, 2009, 01:28 PM

There are a few formulas regarding loagarithms that you need to memorize:

$ log_c(a*b) = log_c(a) + log_c(b) \\ log_c(a/b) = log_c (a) - log_c(b) \\ log_c (a^b) = b * log_c(a) \\ log_c(a) = log_c(b) * log_b(a) $

With these facts you can solve all the problems you posted. I'll help you with the first - use the second formula above, setting b = 5.

estefania · Jan 28, 2009, 10:19 AM

Thank you so much!