Can't figure out equation !!!!!!!!!

**ubhutto** · September 15th 2012, 08:04 PM

The equation that i cannot solve is

(e^x + e^-x) / 2 = 4

**TheEmptySet** · September 15th 2012, 08:07 PM

Originally Posted by ubhutto

The equation that i cannot solve is

(e^x + e^-x) / 2 = 4

Hint: The equation is quadratic in $e^x$

First multiply the equation by $2e^{x}$ This gives

$(e^x)^2+1=8e^{x} \iff (e^{x})^2-8e^{x}+1=0$

If you want you can use the substition $u=e^{x}$ to get the quadratic

$u^2-8u+1=0$

Can you finish from here?

**ubhutto** · September 15th 2012, 08:27 PM

what was your final answer because my equation won't balance

**Prove It** · September 15th 2012, 08:44 PM

Originally Posted by ubhutto

what was your final answer because my equation won't balance

Some better questions:

Did you follow what TheEmptySet told you to do?

Do you know how to solve a Quadratic Equation?

Where exactly did you get stuck?

Why not show your working out? Then we can give you some more guidance.

**ubhutto** · September 15th 2012, 09:03 PM

i figured it out its ln(8-sqrt(60))/2)

**Prove It** · September 15th 2012, 09:29 PM

That is ONE of the two possible answers. What is the other?

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