#Prove convergence and find limit using formal definition

18 messages · Page 1 of 1 (latest)

jolly frost
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Use the formal definition of a limit to prove that each sequence converges, and find
its limit:
$\frac{3n-11}{2n^2+n}$

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jolly frost
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i can reduce it to say it behaves like 1/n but im not sure if thats rigourous enough

cerulean imp
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At the core, you just need to solve for $n$ in $\frac{3n-11}{2n^2+n}<\varepsilon$

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jolly frost
cerulean imp
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You can remove it with inequality tricks. That may be required if you can't define square roots yet

jolly frost
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ok this might be a stupid question, but $|\frac{3n-11}{2n^2+n}|$ cant be represented as $\frac{3n-11}{2n^2+n}$ for all n in IN, so i cant just remove the absolute value function

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jolly frost
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we can define sqrts 👍

jolly frost
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ah gotcha

jolly frost
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@cerulean imp sorry for the ping, but would be correct to say:
$\epsilon 3 n^2 + \epsilon n > 3n - 11$ after some manipulation
$3 \epsilon n + \epsilon > 3 - \frac{11}{n} $ for sufficiently large n become
$3 \epsilon n + \epsilon > 3$ and then solve for n?

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cerulean imp
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that Should work

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I see no issue with it at a glance