Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Differentiate using chain rule

  1. Oct 25, 2007 #1
    Hi everyone,

    I'm new to this forum... I hope I've posted in the right section...

    How do I differentiate y=2e(2x+1) using the chain rule?

    I let u= (2x+1)

    so du/dx = 2

    but how do I differentiate y= 2eU ?

    thank you :)
     
  2. jcsd
  3. Oct 25, 2007 #2

    Hurkyl

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Well, I see a multiplication and an exponentiation in that expression...
     
  4. Oct 25, 2007 #3
    Does it mean that I should use the chain rule again?

    and I get dy/du = 2eU

    so dy/dx = 4e(2x+1) ?
     
    Last edited: Oct 25, 2007
  5. Oct 25, 2007 #4

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    The fact that a problem uses the word "differentiate" does not mean it is a differential equation! I am moving this to the Calculus and Analysis forum.
     
  6. Oct 25, 2007 #5

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    First, do you mean
    [tex]y= 2e^{2x+1}[/itex]
    which in "ASCII" would be y= 2e^(2x+1). What you wrote, I would interpret as 2e times(2x+1) and there is no need for the chain rule!

    If you let u= 2x+1, then, yes, the chain rule says that the derivative of y= 2e^u, with respect to x, is dy/dx= 2e^u (du/dx). Since you have already determined that du/dx= 2, that is dy/dx= 2e^(2x+1) (2)= 4 e^(2x+1). There is no need for a second application of the chain rule.
     
  7. Oct 25, 2007 #6
    thank you very much :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Differentiate using chain rule
Loading...