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Precalculus 15 Online
OpenStudy (anonymous):

Solve each equation below

OpenStudy (anonymous):

\[\log (\frac{ x }{ 10 })=-2+2\log x\]

OpenStudy (anonymous):

\[\log (\frac{ x }{ 10 })=-2+2\log x\] \[\ e^{\log (\frac{ x }{ 10 })}=e^{-2+2\log x}\] \[(\frac{ x }{ 10 })=e^{-2}*e^{2\log x}\] \[(\frac{ x }{ 10 })=e^{-2}*e^{\log x^{2}}\] \[(\frac{ x }{ 10 })=e^{-2}*x^{2}\] \[e^{-2}*x^{2}-\frac {x} {10} =0\] \[x(e^{-2}*x-\frac{1}{10})=0\] \[x=0\] or \[x= \frac{e^{2}}{10}\]

OpenStudy (anonymous):

e = 10

OpenStudy (anonymous):

wow...okay

OpenStudy (anonymous):

It looks so simple once it's all solved but i cant ever quite get it...

OpenStudy (anonymous):

if there's a log you have to raise both sides by the base.

OpenStudy (anonymous):

no matter what?

OpenStudy (anonymous):

well, if you have log = log then you can just take the log out. for example: log (5x+3)=log (2), goes to 5x+3 = 2

OpenStudy (anonymous):

okay that makes sense. Mind helping with the next one?

OpenStudy (anonymous):

sure

OpenStudy (anonymous):

*phew* okay! \[\sqrt{3x+6}-x-2=0\]

OpenStudy (anonymous):

I feel like its pretty straight forward and I come close to the answer but its never quite right. this is what I did.

OpenStudy (anonymous):

And i just accidentally deleted everything...

OpenStudy (anonymous):

but i ended up with 0=x^2+x-2

OpenStudy (anonymous):

\[\sqrt{3x+6}-x-2=0\] \[\sqrt{3x+6}=x+2\] \[(\sqrt{3x+6})^{2}=(x+2)^{2}\] \[{3x+6}=(x+2)*(x+2)\] \[3x+6=x^{2}+4x+4\] \[x^{2} + x - 2 = 0\] \[(x+2)(x-1)=0\] \[x= -2, x=1\] but now you have to check your answers \[\sqrt{3(-2)+6}-(-2)-2=0\] \[\sqrt{-6+6}+2-2=0\] \[\sqrt{0}+0=0\] ture, x=-2 is an answer, \[\sqrt{3(1)+6}-(1)-2=0\] \[\sqrt{9}-3=0\] \[3-3=0\] ture, x=1 is answer, therefore: x= 1 and x= -2

OpenStudy (anonymous):

So i was on the right track i just missed that last step...darn. So close....

OpenStudy (anonymous):

okay another seemingly straightforward one...\[\sqrt{t+7}-\sqrt{t}=1\]

OpenStudy (anonymous):

When I look at it the first thing i do is \[(\sqrt{t+7}-\sqrt{t}=1)^{2}\]

OpenStudy (anonymous):

but if you do that you end up with 7=1 which isnt right of course.

OpenStudy (anonymous):

more the sqrt (t) to the other side before you square both side

OpenStudy (anonymous):

thank you so much...Like i said so close but so far away...

OpenStudy (anonymous):

\[t+7 = t+ 2\sqrt{t} +1\] \[3 = \sqrt{t}\] t= 9 then go back and check it

OpenStudy (anonymous):

wait, where did the t+2tsqrd come from?

OpenStudy (anonymous):

\[(\sqrt{t+7}=1+\sqrt{t})^{2}\] \[t+7 = (1+\sqrt{t})^{2}\] \[t+7 = t+ 2\sqrt{t} +1\]

OpenStudy (anonymous):

ohhhh okay so then you subtract t and 1, then divide both sides by 2 then boom. 9.

OpenStudy (anonymous):

ya, i was doing it quickly,

OpenStudy (anonymous):

i got to get to class now. good luck.

OpenStudy (anonymous):

thanks so much.

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