#Prove a limit equality

21 messages · Page 1 of 1 (latest)

vast phoenix
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Prove that
lim_n->∞ (4n^2 + 1)/(3n^2 + 2) = 4/3
by using the epsilon delta definition

chilly kiteBOT
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queen abyss
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Why do you need the epsilon-delta proof?

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Although one could arguably say that:
$$\frac{4n^2+1}{3n^2+1} = \frac{4}{3} \times \frac{1 + \frac{1}{4n^2}}{1 + \frac{2}{3n^2}}$$

indigo sandBOT
queen abyss
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So taking the candidate limit L:
$$\frac{4n^2+1}{3n^2+1} - L = \frac{4}{3} \left( \frac{1 + \frac{1}{4n^2}}{1 + \frac{2}{3n^2}}-1 \right)$$

indigo sandBOT
queen abyss
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I think you can work your way from there with some inequality tricks

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I'll let you try out

vast phoenix
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What is the candidate limit and why are you subtracting it?

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The problem has a constraint to use the definition

queen abyss
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that's what you said in the question

vast phoenix
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And why are you subtracting it?

queen abyss
hearty kestrel
vast phoenix
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f(x) tends to L as x -> c iff For any epsilon > 0 there is some delta > 0 such that for any x (0 < |x - c| < delta => |f(x) - L| < epsilon)

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Is that correct?