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Mathematics 13 Online
OpenStudy (anonymous):

Help? logs.

OpenStudy (anonymous):

what logs?

OpenStudy (anonymous):

yea what logs

OpenStudy (anonymous):

http://web2.0calc.com/ Rose for then your doing logarithmic form try useing that calc

OpenStudy (anonymous):

logarithmic form Is a other type of math equations

OpenStudy (anonymous):

or logs

OpenStudy (anonymous):

\[\log_{9}(-11x+2)=\log_{9}(x^{2}+30)\] Do I divide by \[\log_{9} \] on both sides? I need to find x

OpenStudy (anonymous):

no you don't divide

OpenStudy (anonymous):

you subtract

OpenStudy (anonymous):

No I divide because it's opposite of multiplying.

OpenStudy (anonymous):

1- log(A-B)=logA/logB

OpenStudy (anonymous):

yes you got it

OpenStudy (anonymous):

In Logs, we don't say like that..

OpenStudy (anonymous):

2- bring log x in one side

OpenStudy (anonymous):

we say, "take the antilogarithm" on both sides..

OpenStudy (anonymous):

It is simple, don't make it hard..

OpenStudy (anonymous):

@AJ01 you're not making sense @waterineyes then how do I do it?

OpenStudy (anonymous):

you have log base 9, on both the sides, so take antilog: \[If \quad \ln_a(x) = \ln_a(y), \ \ then \ \ x = y\]

OpenStudy (anonymous):

So: \(\log_9(-11x+2) = \log_9(x^2 +30)\) \(\implies -11x + 2 = x^2 + 30\)

OpenStudy (anonymous):

Now, this is just a quadratic equation, find \(x\)..

OpenStudy (anonymous):

@AJ01 Also this is correct formula: \[\log(a) - \log(b) = \log(\frac{a}{b})\]

OpenStudy (anonymous):

So I use the quadratic equation \[x=\frac{ -b \pm \sqrt{b^{2}-4ac} }{ 2a }\] \[x^{2}+11x+28\]

OpenStudy (anonymous):

\[x=\frac{ -11 \pm \sqrt{11^{2}-4*1*28} }{ 2*1 }\]

OpenStudy (anonymous):

you can also use Factorization Method if you want.. 7 and 4 are the factors..

OpenStudy (anonymous):

\[x^2 + 11x + 28 = 0 \\ (x+7)(x+4) = 0 \\ x = -7 \quad or \ \quad x = -4\]

OpenStudy (anonymous):

Getting??

OpenStudy (anonymous):

Oh right! I always forget about factoring.

OpenStudy (anonymous):

Good..

OpenStudy (anonymous):

Could you help me with another. It's a little different.

OpenStudy (anonymous):

Sure..

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