1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Expansion of exponentials (very easy)

  1. Apr 30, 2008 #1
    Sorry, i'm having a severe mental block here, sorry if this is laughable.

    Question
    Expand (e^x + e^-x)^2

    I've got the answer but i'm just stumped at how to reach it, I dunno where the 2 comes from:

    Answer
    e^2x + 2 + e^-2x

    Thanks (and sorry again)
     
  2. jcsd
  3. Apr 30, 2008 #2
    Are you unsure how to even start or is there a particular term you are confused about? Which 2 are you talking about, the +2 or the 2 in e^2x?
     
  4. Apr 30, 2008 #3
    Sorry, the +2. I can reach the e^2x + e^-2x but I can't reach the "+2" which means the method I'm using is incorrect.

    I haven't touched this stuff in a while so I'm just trying to re-remember it.
     
  5. Apr 30, 2008 #4
    Remember, (a+b)^2 = a^2 + 2ab + b^2 (use foil), NOT a^2 + b^2
     
  6. Apr 30, 2008 #5
    Yeah, i tried using foil.

    Foil if I'm not mistaken would grant me.

    (e^x + e^-x) (e^x + e^-x)

    (e^x * e^x) + (e^x * e^-x) + (e^-x * e^x) + (e^-x * e^-x)

    (e^2x) + (1) + (1) + (e^-2x)

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

    Is that right?
     
  7. Apr 30, 2008 #6
    Yep, looks good.
     
  8. Apr 30, 2008 #7
    aha, thanks for the help. Just got a bit confused with the powers for a moment it seems.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Expansion of exponentials (very easy)
  1. Easy exponential decay (Replies: 8)

  2. Isolate L, very easy (Replies: 5)

  3. Very Easy DE (Replies: 3)

Loading...