how to find zeros of ln's

**Jasmina8** · October 22nd 2009, 01:54 PM

So my problem is: f(x)= -2+ln(x^2)

I need to find the zeros of f and to figure out for what real numbers x is f defined. If anyone can explain to me how to do this I would really appreciate it. Thanks in advance!

**tonio** · October 22nd 2009, 01:58 PM

Originally Posted by Jasmina8

So my problem is: f(x)= -2+ln(x^2)

I need to find the zeros of f and to figure out for what real numbers x is f defined. If anyone can explain to me how to do this I would really appreciate it. Thanks in advance!

$-2+\ln x^2 = 0 \Longleftrightarrow \ln x^2=2 \Longleftrightarrow x^2=e^2 \Longleftrightarrow |x| =e$

Tonio

**Defunkt** · October 22nd 2009, 02:00 PM

$f(x) = 0\Rightarrow 2 = ln(x^2) \Rightarrow e^2 = e^{ln(x^2)}$

Can you finish?

Ah, I see I'm late... never mind!

**Jasmina8** · October 22nd 2009, 02:06 PM

how do you get e^lnx^2 ?? I would really like if you can EXPLAIN to me how to get the answer. Thank you

**tonio** · October 22nd 2009, 02:31 PM

Originally Posted by Jasmina8

how do you get e^lnx^2 ?? I would really like if you can EXPLAIN to me how to get the answer. Thank you

If you deal with these things you should at least know their definition, otherwise it'll be easy to fall into desperation and helplessness:

$\log_a{b}=x \Longleftrightarrow a^x=b$

Now just remember that $\ln x=\log_e{x}$

Tonio

**Jasmina8** · October 22nd 2009, 02:48 PM

I got it now. Thank you for your help.

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how to find zeros of ln's

uhh.

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