Holy shit guys, CalcI can never, ever be construed as "hard". It just doesn't happen. If you want to see hard, try (Real) Analysis I.
I never understood the teaching of epsilon-delta in calcI. In most cases, you don't prove anything useful with it. You just do some silly shit where you like verify that the limit as x->2 of 2*x is 4. Wow, yay. Introducing epsilon-delta seems to obscure the key concepts by burying them under intimidating mathematical notation.
OP: might be easier to help if you could post your current understanding of epsilon-delta limits. What's the definition? If I draw a picture of f(x), what does that definition mean graphically? Suppose I want to prove something obvious, like the limit as x->2 of f(x) = 2*x is 4. How would you try to do it? Maybe these things are all obvious/easy to you... my point is that it'd help us to understand what you don't understand.
Sure, thanks.
Suppose I'm given a graph of f(x)= (5x-4), finding the limit as x approaches 2.
I could tell you the limit was 6.
I know that the epsilon is the range in y-values, corresponding to the delta change in x.
I could also tell you that the delta I would chose, for this problem, would be e/5. I got that from simplifying down the epsilon side until I got
(x-2)<e/5. However, from there I am not sure what to do, as in how to prove it.
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Given another problem: lim (x^2+x-11)=9 as x approaches 4.
I get the epsilon side down to
|x+5||x-4|<e and 0<|x-4|<delta.
From here,
1) I need to get rid of the "X+5" on the epsilon inequality.
2) How do I prove it?
....fuck