# Thread: natural log

1. ## natural log

$\displaystyle e^x+e^{-x}=3$

How do you solve for x here?

2. Originally Posted by DarthBlood
$\displaystyle e^x+e^-x=3$

(note: that's e to the negative x power, i just don't know how to show that, sorry.)

How do you solve for x here?
BTW: If you have more than one character in an exponent, set off the whole exponent in braces.
$$e^{-x}$$ gives $\displaystyle e^{-x}$ instead of $\displaystyle e^-x$.

3. Originally Posted by DarthBlood
$\displaystyle e^x+e^{-x}=3$
How do you solve for x here?
$\displaystyle e^x+e^{-x}=3$ multiply by $\displaystyle e^x$.
$\displaystyle e^{2x}-3e^x+1=$.

Can you solve $\displaystyle w^2-3w+1=0?$
If so let $\displaystyle z=e^x$.

4. Originally Posted by Plato

Can you solve $\displaystyle w^2-3w+1=0?$
errr....no sorry.

5. For $\displaystyle ax^2+bx+c=0$

$\displaystyle x = \frac{-b\pm \sqrt{b^2-4ac}}{2a}$

6. Originally Posted by Plato
$\displaystyle e^x+e^{-x}=3$ multiply by $\displaystyle e^x$.
$\displaystyle e^{2x}-3e^x+1=$.
Can you solve $\displaystyle w^2-3w+1=0?$
If so let $\displaystyle z=e^x$.
Originally Posted by DarthBlood
errr....no sorry.
May I, with all due respect, ask this question?
If you cannot do a basic beginning algebra question, then why are you being asked to do an advanced algebra question involving exponentials?

7. There's my problem: I keep forgetting to add "with all due respect"!

8. lol i've forgotten everything over the summer break...i honestly forgot that i could use that equation to solve it.