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Proving using ε/δ definition

  • Thread starter cwz
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  • #1
cwz
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Homework Statement


Prove using ε/δ definition,

lim x tends to -1 (x^3+2x^2) = 1


Homework Equations





The Attempt at a Solution


I have done to the step where δ(δ^2-δ-1) ≤ δ ≤ ε

so i choose ε=min(2,ε)

Not sure whether I am correct or not
 

Answers and Replies

  • #2
vela
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I hope you realize that
$$\lim_{x \to -1} (x^3+2x^2) \ne 1$$ so you're going to have a tough time proving it. In any case, you need to show more of your work. We can't see your paper or read your mind to see what you actually did.
 
  • #3
pasmith
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i hope you realize that
$$\lim_{x \to -1} (x^3+2x^2) \ne 1$$
[itex](-1)^3 + 2(-1)^2 = -1 + 2 = 1[/itex]. Last time I checked, [itex]x^3 + 2x^2[/itex] was continuous everywhere.
 
  • #4
vela
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Well, now I feel like an idiot. :wink: And I checked it over and over and kept getting -1.
 

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