Logarithm help :( pweeeeeeeeease?
Logarithm help :( pweeeeeease?
What do you do to get rid of subtraction to get rid of subtraction or addition inside of natural logs?
For example,
lna=2
lnb=3
lnc=5
ln(a-4/b^1c^2)=?
I can get it to be:
ln(a-4) - (lnb+2lnc)
Then I get stuck. I don't know what to do with the a-4 in that first log.
The answer to the problem is apparently -21, I don't understand how they got that.
Here is another problem:
lnx + lnx-3 =ln(2x)
x=?
Turns out x=5, but again now idea how they got that.
This is online homework in which showing work is not necessary, but I need to know how to do these problems.
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Answers & Comments
OK check this out...
The question does make sense, but as stated there is no answer.
in most "log" questions you are asked to either simplify something, or solve something.
normally you will end up with this log addition type of situation that you are having trouble with.
In some cases the solution will be to pull out the calculator and simply do the logs on it and give the answer
x = log (2 + 3)
BUT there is another twist that math teaches pull on students ....
lnx + lnx-3 =ln(2x)
in this case the problem is more of a math basic property manipulation then solviing...
follow this...
lnx + lnx-3 =ln(2x)
lnx =ln(2x) - lnx-3
use log subtractin = division property
ln x = ln (2x/x-3)
HERE IS WHERE THE LOG GO AWAY !!!
if x ^ n = x^3+1 ... you know n would = 4 !
so in your problem x = 2x/x-3 IT IS NOW A ALGEBRA problem
x^2 - 3x = 2x
x^2 = 5x
divide by x
x = 5 !!!!!!!!!