#fp`1

79 messages · Page 1 of 1 (latest)

supple wadi
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part e

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so i got the ans right, bcs, what else u gonna say

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but, if k not 2, then u get infinity aS ANSWER

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If lim x--> 0 of f(x) = infinity, does that mean it 'doesnt exist'? I thought doesnt exist means indeterminate means 0/0 or infinity/infiniftyy

iron echo
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is this pure further maths?

iron echo
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(if the question youre asking is what if we have 0/0)

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that 0/0 is an indeterminate form as anything can be multiplied by 0 to get 0 so we have to do more work and cant simply say it tends to infinity

supple wadi
supple wadi
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why must k=2

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we have (2-k)/x

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  • constant
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because all other terms have an x term in them

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for lim x-->0 of (2-k)/x

the question claims that, k=2

whats wrong with lim x-->0 k/x =inf?

iron echo
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ohhhh

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because thats infinity right

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and we want the expression to EXIST

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cuz the que says that if u read at the bottom

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and the expression only exists WITH those limits if the LIMIT allows the expression to be FINITE so to converge

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and IF we do wat you propose, it would DIVERGE and be infinite

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is that helpful??

supple wadi
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L=0 exists

Abs L=inf does not exist

iron echo
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wats abs?

supple wadi
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Absolute

supple wadi
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Modulus

iron echo
supple wadi
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L is just notation I saw in Wikipedia

iron echo
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ohhhh yh positive or negative infinity doesnt matter

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like we dont rlly deal with it at alevel fm

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only if e is to the negative x and then lim x --> infinity

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but thats not negative infinity

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but getting back to the main que we were speaking abt

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if the limit makes expression tend to infinity

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then THAT expression does NOT exist, it diverges

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like in improper integrals?

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yk that topic?

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so for this que we WANT the expression to exist and k is a constant cuz it says it above so if we find the value for which we get 0 on the top then when lim x --> 0 we get 0/0 which is NOT infinity it is just indeterminate form so essentially it has a value but we dont know it and as far as fm alevel we dont ever really have to find it or do anything with it

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so if the numerator is 0 thats the only time we can get the full expression to be finite

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do u understand?

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ik im waffling a lot and repeating points but idk any other way to explain it

subtle gull
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it can be a bit ambiguous

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but converge, diverge, doesnt exist should all be different

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i think you CAN say exists but diverges

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however in this case it doesnt work

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because lim x->0 k/x is not infinity

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if you approach 0 from the right it is

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but from the left its -inf

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so it doesnt exist because the limits from both sides are different

iron echo
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no

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it only exists when k=2

subtle gull
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yeah

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which is what ive said

iron echo
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oh right

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mb

supple wadi
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thansk for effort though

supple wadi
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Therefore

the set of all convergent limits, is a subset of the set of all existing limits

but they are not the same set (so not vice versa)

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ye?

subtle gull
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I would say yes

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But honestly I do think it’s ambiguous and some people will say convergence and existence are the same

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Maybe context dependant which isn’t a very good answer

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If you just stick with convergence = existence you can’t go wrong really so maybe don’t worry about this

elder granite
iron echo
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bro is arguing with a shadow

supple wadi
iron echo
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water under the bridge

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not that deep