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Mathematics 7 Online
OpenStudy (anonymous):

Is this equation true? please help!

OpenStudy (anonymous):

\[4 \log_{3} x+ \frac{ 1 }{ 2 } \log_{3} y-2 \log_{3}2= \log_{3} \frac{ x^4\sqrt{y} }{ z^2 }\]

OpenStudy (phi):

it looks like you have a typo in the last term on the left side of the equal sign.

OpenStudy (phi):

to find out, use the rules: \[ \log(a\cdot b) = \log(a)+\log(b) \] \[ \log(\frac{a}{ b}) = \log(a)-\log(b) \] \[ \log(a^b) = b\log(a) \]

OpenStudy (phi):

apply the rules to the right-hand side

OpenStudy (anonymous):

what would be the a and the b?

OpenStudy (phi):

match a and b to terms in the problem. For example you could say a= x^4 sqrt(y) and b is z^2 now use the 2nd rule

OpenStudy (phi):

what do you get if you match a= x^4 sqrt(y) and b is z^2 and then use the 2nd rule ??

OpenStudy (anonymous):

i really dont understand what the process is

OpenStudy (phi):

The way to interpret this rule: \[ \log(\frac{a}{ b}) = \log(a)-\log(b) \] look at your problem \[ \log(\frac{x^4 \sqrt{y}}{z^2}) \] if you call all of the stuff in the top a and the stuff in the bottom b, you can rewrite your problem as log(a)- log(b) but replace a with "stuff in the top" and b with "stuff in the bottom" can you do that?

OpenStudy (anonymous):

\[\frac{ \log x^4\sqrt{y} }{ \log z^2}\]

OpenStudy (phi):

there is NO RULE that says \[ log\left( \frac{a}{b}\right) = \frac{log(a)}{log(b)}\]

OpenStudy (phi):

which is what you did. you should use \[ log\left(\frac{a}{b}\right) = log(a)- log(b) \]

OpenStudy (phi):

the idea is you give the name "a" to the complicated \( x^4 \sqrt{y}\) and the name "b" to \(z^2\) the rule says if you see a divided by b inside a log, like this \[ log\left(\frac{a}{b}\right) \] you can write it like this instead \[ log(a)-log(b) \] but you can replace the names "a" and "b" with the complicated stuff...

OpenStudy (phi):

try again

OpenStudy (anonymous):

\[\log x^4\sqrt{y} - \log z^2\]

OpenStudy (phi):

yes. very good.

OpenStudy (phi):

as practice, try using the 3rd rule \[ \log(a^b) = b\log(a) \] on the last term \(-\log(z^2) \)

OpenStudy (phi):

I would let a be the name of z and b be the name of 2.

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