# Thread: Can't figure out equation !!!!!!!!!

1. ## Can't figure out equation !!!!!!!!!

The equation that i cannot solve is

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

2. ## Re: Can't figure out equation !!!!!!!!!

Originally Posted by ubhutto
The equation that i cannot solve is

(e^x + e^-x) / 2 = 4
Hint: The equation is quadratic in $\displaystyle e^x$

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

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

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

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

Can you finish from here?

4. ## Re: Can't figure out equation !!!!!!!!!

Originally Posted by ubhutto
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.

5. ## Re: Can't figure out equation !!!!!!!!!

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

6. ## Re: Can't figure out equation !!!!!!!!!

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