1. Limited time only! Sign up for a free 30min personal 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!

Epsilon Dellta Proof

  1. Oct 20, 2009 #1
    Okay so here's the limit lim(as x --> -1) 2x^2=2

    I have |2x^2-2| < 1
    2|x + 1||x - 1| < 1
    |x + 1||x - 1| < 1/2

    and 0 < |x + 1 | < delta
    -1 - delta < x < -1 + delta
    |x - 1| < -2 + delta

    |x + 1| < 1/2(-2 + delta)

    so is delta = 1/2(-2 + delta) correct? if so, how do i know which answer (since there will be 2) is right?
     
  2. jcsd
  3. Oct 20, 2009 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi evry190! :smile:

    (have a delta: δ and an epsilon: ε :wink:)

    Where's your ε?

    (an epsilon delta proof has to have an epsilon …

    the clue's in the name! :biggrin:)​

    Start again, and try to prove that |2x^2-2| < ε. :smile:
     
  4. Oct 22, 2009 #3
    but in the problem the epsilon is 1
     
  5. Oct 23, 2009 #4

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    I don't understand … the problem was "the limit lim(as x --> -1) 2x^2=2" …

    where's the ε = 1 in that? :confused:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Epsilon Dellta Proof
  1. Epsilon-Delta Proof (Replies: 3)

  2. Delta epsilon proof (Replies: 5)

Loading...