# A variable raised to a power that contains that variable, all equal to one?

• Sep 23rd 2011, 04:35 PM
MRich520
A variable raised to a power that contains that variable, all equal to one?
I put the following problem into Wolfram Alpha and found that the solutions are the square root of e and 1. Can somebody explain how you'd solve it to get both of those answers? I only got the square root of e. Here's the problem:

x^(ln(x) - 0.5) = 1

It makes sense to me that 1 works as well, but am I missing some kind of rule that would have made me get 1 when I solved it the first time around?
• Sep 23rd 2011, 04:58 PM
Plato
Re: A variable raised to a power that contains that variable, all equal to one?
Quote:

Originally Posted by MRich520
x^(ln(x) - 0.5) = 1

I am glad that $x=1$ works for you.

Now do you agree that $(\sqrt{e})^0=1~?$
If you do then what does $\ln(\sqrt{e})=~?$
• Sep 23rd 2011, 05:30 PM
MRich520
Re: A variable raised to a power that contains that variable, all equal to one?
Quote:

Originally Posted by Plato
I am glad that $x=1$ works for you.

Now do you agree that $(\sqrt{e})^0=1~?$
If you do then what does $\ln(\sqrt{e})=~?$

$\ln(\sqrt{e})=1/2$

Eh...I'm not sure if that was the answer you were asking for. Mind clarifying?
• Sep 23rd 2011, 05:54 PM
Plato
Re: A variable raised to a power that contains that variable, all equal to one?
Quote:

Originally Posted by MRich520
$\ln(\sqrt{e})=1/2$
Eh...I'm not sure if that was the answer you were asking for. Mind clarifying?

Well what is $\ln(\sqrt{e})-0.5~?$
And what is $\sqrt{e}$ to that power?
• Sep 23rd 2011, 08:17 PM
Soroban
Re: A variable raised to a power that contains that variable, all equal to one?
Hello, MRich520!

Quote:

$\text{Solve for }x\!:\;\;x^{(\ln x - \frac{1}{2})} \:=\: 1$

Take logs: . $\ln\left(x^{(\ln x - \frac{1}{2})}\right) \:=\:\ln 1$

We have: . $\left(\ln x - \tfrac{1}{2}\right)\cdot \ln x \:=\:0$

And we have two equations to solve:

. . $\begin{array}{ccccccc}\ln x - \tfrac{1}{2} \:=\:0 & \Rightarrow & \ln x \:=\:\tfrac{1}{2} & \Rightarrow & x \:=\:e^{\frac{1}{2}} \\ \\ \ln x \:=\:0 & \Rightarrow & x \:=\:e^0 & \Rightarrow & x \:=\:1 \end{array}$

• Sep 28th 2011, 02:35 PM
MRich520
Re: A variable raised to a power that contains that variable, all equal to one?
Quote:

Originally Posted by Soroban
Hello, MRich520!

Take logs: . $\ln\left(x^{(\ln x - \frac{1}{2})}\right) \:=\:\ln 1$

We have: . $\left(\ln x - \tfrac{1}{2}\right)\cdot \ln x \:=\:0$

And we have two equations to solve:

. . $\begin{array}{ccccccc}\ln x - \tfrac{1}{2} \:=\:0 & \Rightarrow & \ln x \:=\:\tfrac{1}{2} & \Rightarrow & x \:=\:e^{\frac{1}{2}} \\ \\ \ln x \:=\:0 & \Rightarrow & x \:=\:e^0 & \Rightarrow & x \:=\:1 \end{array}$

Thanks!

I should know that from my classes :p.

And sorry Plato I forgot to respond :(