Solve

Question

0=e^3x-9e^2x+20e^x

Answer 1

You may find this easier if you let u = e^x. Then you have

u^3-9u^2+20u = 0
u(u^2-9u+20) = 0

I think you can probably factor that.

Of course, one solution is
u=0, or e^x = 0
But that never happens, so you can throw it out.