Derivative Problem

  • Thread starter Eshi
  • Start date
  • #1
27
0

Homework Statement


I have to find the min and max of this function using derivatives:

(e^(-x)) - (e^(-2x))




The Attempt at a Solution


f'(x) = -e^(-x) + 2x(e^(-2x))
So now i set that to zero, and I get...

2x(e^(-2x)) = e^(-x)

And at this point I have no idea what to do. If you divide e^-x by e^-2x can u do something with the exponents?
 

Answers and Replies

  • #2
135
0
Double check your derivative, you shouldn't be bringing an x down right? The derivative of ecx for a constant c is just cecx
 
  • #3
27
0
o i ggot it! so it become

2 = e^(-x-2x)
and then you simply take the ln...

thanks jeffreydk
 
  • #4
135
0
No problem.

Watch out though, I think you have a sign error in there.

f'(x)=-e-x+2e-2x=0

So then 2e-2x=e-x

and therefore by dividing you get 2=e-x+2x
 

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