Solving Log functions... x + 7 / x - 9 = 11

Complex numbers, rational functions, logarithms, sequences and series, matrix operations, etc.
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Joined: Mon Feb 23, 2009 4:27 pm

Solving Log functions... x + 7 / x - 9 = 11

Postby Merz » Mon Feb 23, 2009 4:29 pm

I forgot some of my algebra and can't recall what to do with x+7/x-9=11...

nearly done.

Posts: 35
Joined: Tue Dec 16, 2008 7:47 pm

Re: Solving Log functions...

Postby DAiv » Mon Feb 23, 2009 7:28 pm

Hi Merz, welcome to the forums. :wave:

As written, the equation you gave was , which I presume you meant rather than , (x+7) / (x-9) = 11. In either case, you don't need logs to solve these.

So, assuming you did mean the first version, I'll take you part way and give you a pointer for the rest. (If you didn't mean that version, let me know and I'll post a reply for the other one.)

Solve for :

Add 9 to both sides:

Get rid of the fraction on the left hand side by multiplying both sides by :

... and multiplying out the parentheses:

Bring the over and rearrange:

And now you're left with a quadratic equation.

Can you continue from there?


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