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OpenStudy (anonymous):

@phi @mathmale

OpenStudy (anonymous):

Solve. \[16^{d-4} = 3^{3-d}\]

OpenStudy (phi):

are you studying logarithms ?

OpenStudy (anonymous):

yes

OpenStudy (phi):

do you know this rule: \[ \log(a^b) = b\log(a) \] ? You should first "take the log" of both sides of the equation then use that rule

OpenStudy (anonymous):

on my online classs I cant see the lesson so I come on this site

OpenStudy (phi):

the first step is "take the log" of both sides. that means if you have a = b take the log means write log(a) = log(b) can you do that for your equation (just write in the log)

OpenStudy (anonymous):

is 16 the a and 3 the b

OpenStudy (phi):

a stands for the "entire left side" b is the right side

OpenStudy (anonymous):

16 d−4 is ? and 3 3−d is b?

OpenStudy (phi):

yes

OpenStudy (anonymous):

ok now what do we do

OpenStudy (phi):

the idea is if left_side = right_side then the log of the left_side equals the log of the right_side log( left_side ) = log(right_side)

OpenStudy (phi):

you should now have \[ \log\left( 16^{d-4}\right) =\log\left( 3^{3-d}\right) \]

OpenStudy (anonymous):

ok I got that now

OpenStudy (phi):

now use \[ \log(a^b) = b\log(a) \] here "b" stands for the entire exponent (no matter how complicated) use that rule on both sides. what do you get ?

OpenStudy (anonymous):

im not sure can you go through it please

OpenStudy (anonymous):

like I saw the work I don't know the answer

OpenStudy (phi):

It's worth learning how to interpret this rule. Do "pattern matching" in \[ \log(a^b) = b\log(a) \] the "a" matches up with the base "b" matches with the exponent. can you match a and b to your problem \[ \log\left( 16^{d-4}\right) \]

OpenStudy (anonymous):

\[ \log\left( 16^{d-4}\right) \] what is that

OpenStudy (anonymous):

its confusing me

OpenStudy (phi):

at the very top you say *** solve. \[ 16^{d-4} = 3^{3-d} \] **** is that what we have to do ?

OpenStudy (anonymous):

yea but on my computer it comes up as a bunch of slashes and numbers

OpenStudy (phi):

what about this log( 16 ^ (d-4) ) match that to log( a^b) what does "a" match up with? what does "b" match up with ?

OpenStudy (anonymous):

that's better

OpenStudy (anonymous):

would match up to log16 ^ (d-4) )

OpenStudy (phi):

we want to use the rule log( a^b) = a log(b)

OpenStudy (anonymous):

can you tell me what the answer is and then tell me how you go it

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