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Mathematics 6 Online
OpenStudy (anonymous):

solve the following log equation question below

OpenStudy (anonymous):

\[\log_{3}x+\log_{3}(x-8)=2 \]

OpenStudy (phi):

the first step is use the rule \[ \log(a)+\log(b)= \log(a\cdot b) \] in other words, you can replace the addition of two logs (of the same base) with one log, where you multiply. can you do that ?

OpenStudy (anonymous):

yea i got that so far

OpenStudy (phi):

what do you have so far ?

OpenStudy (anonymous):

x^2-8x inside log

OpenStudy (phi):

\[ \log_3(x^2-8x) = 2\] make each side the exponent of the base 3: \[ 3^{\log_3(x^2-8x)} = 3^2\] and use the rule \[ a^{log_a(b)} = b \] to simplify the left side. in other words, 3 to the power log base 3 "undoes" the log

OpenStudy (anonymous):

do you end up with just x^2-8x=9

OpenStudy (phi):

yes

OpenStudy (anonymous):

ok cool then factor and x=-1 cant be in the solution so its just 9

OpenStudy (phi):

yes

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