Math problem help (quiz due today) logs?

Marishka · 07-27-2008

Okay, I can't figure out this one math problem & I've already screwed it up twice...

Somehow
logx-log(x+15)=2
x=5

&

logx-log(x-15)=2
x=20

And I can't find how they came up with that because the instructions for the problem type leave me with crazy random stuff like x=-10 or x=30...

So anywho, the next question I have is logx-log(x+9)=1
and I have NO IDEA how to get it right.

Any help would be appreciated, thanks!
my TI-89 is pretty much retarded, and "where I got that" is in the online-based quiz for my precalc class... I don't know how they managed that, but the instructions for that type of problem lead me to a VERY messed up answer.
SINCE I was already in the quiz and it would've thrown me out (I expected more answers in that short amount o time) I guessed based on a logical pattern I thought I saw, but APPARENTLY logx+log(x+9)=1 is equal to x=1!!! Who'd have thunk it???

Alfred Sauce · 07-27-2008

Where did you find that

logx-log(x+15)=2
x=5

This is not correct, try plugging into a calculator.