solve ln(x+2)+ln(x-1)=1 it can be written as (x+2)(x-1)=e apparently What rule is this? and the answer is x = (sqrt[9+4e]-1)/2
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note the sum rule for logs ... change the log equation to an exponential ...
o ok. how do u change it to an exponential? just put e as the base and it gets rid of ln? and how did he get that answer? i put it into the quadratic formula but am not getting that same one.
Originally Posted by Shadowfox1 o ok. how do u change it to an exponential? just put e as the base and it gets rid of ln? and how did he get that answer? i put it into the quadratic formula but am not getting that same one. You should know that is equivalent to .
, , since ...
ooooooo very true. thx a lot
Last edited by Shadowfox1; Oct 14th 2008 at 03:37 PM.
wait, but how do u know x>1?
... what is the domain?
o ok, i see. I can never find the domain without a calculator.
I can never find the domain without a calculator. learn the concept of domain of a function ... the "machine" will put you at a great disadvantage.
yea true, i should. its just hard when you get stuff involving e and log and stuff like that
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