Homework Help: Solve e^(3x)+sinh(x)=0 ?

1. Jul 11, 2010

System

1. The problem statement, all variables and given/known data

Solve the following equation for x:

$$e^{3x}+sinh(x)=0$$

2. Relevant equations

None.

3. The attempt at a solution

It the same as:

$$e^{3x}+\frac{e^{2x}}{2}-\frac{e^{-2x}}{2}=0$$

Multiply by 2

$$2e^{3x}+e^{2x}-e^{-2x}=0$$

Multiply by e^(2x)

$$2e^{5x}+e^{4x}=1$$

then I stopped.

2. Jul 11, 2010

Karmalo

I think $$sinh(x)=\frac{e^{x}}{2}-\frac{e^{-x}}{2}$$

3. Jul 11, 2010

niklaus

sinh(x) = 1/2(e^x - e^(-x))

Looks to me like you should be able to get a quadratic equation out of that...

4. Jul 11, 2010

System

ohhhh
sorry
:|
I finished it
thanks <3