Math Is Fun Forum

Kiran

Member

Registered: 2006-11-15

Posts: 177

solve for x

log(2x + 1) = 3log2 - log4

i did

log2x + log1 = 3log2 - log4
log2x + log1 = 0.301029995
subtract log1 from both sides
log2x = 0.30102995
divide by log2
x = 1

correct?

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Zhylliolom

Real Member

Registered: 2005-09-05

Posts: 412

Re: solve for x

log(2x + 1) ≠ log 2x + log 1.

You can simplify the right hand side using the following rules of logarithms:

b log a = log a[sup]b[/sup].
log a - log b = log(a/b).

Then when you have an expression on the right hand side that is in terms of a single logarithm, you can cancel out the logarithms:

log a = log b  =>  a = b.

So you will end up with 2x + 1 = something. I will leave it up to you to work out the details! Good luck.

basmah

Member

Registered: 2006-10-02

Posts: 18

Re: solve for x