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Where can I find a good explanation of the $\epsilon - \delta$ definition of a limit. I have tried looking at my textbook and it doesn't make much sense, and I have also looked on Google as well looking for a definition. Or maybe someone can explain it on here? I really want to understand the definition of it, but I cant seem to find an explanation that makes sense to me.

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    So then is the limit definition used for proving that a limit exists at a specific L? Or can it be used to actually find the limit of some function? I would assume both, however I don't quite see how you would use it to actually find the limit. @BabakSorouh I looked in a textbook but it didn't explain it in a way that made sense to me which is why I'm asking on here.2012-10-22

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So the definition says: $\lim_{x \to a}f(x) = L$ means: for all $\epsilon >0$, there exists a $\delta >0$ such that $0<|x - a| < \delta \Rightarrow |f(x) - L| < \epsilon $

To understand this definition, you have to know about quantifiers: (for all, there exists). In other words, If for every $\epsilon$, you are able to find a suitable $\delta$, then this proves the limit of $f$ is $L$. When you see in a statement, the word (THERE EXISTS), That means you need to find, to construct and so proving its existence. In this case, you have to find a $\delta$.

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    And this definition is also wrong, according to the most common textbooks. The condition on $x$ must be rewritten as 0<|x-a|<\delta, otherwise many limits will not exist.2012-10-22