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Mathematics 22 Online
OpenStudy (anonymous):

Find the limit if one exists. lim x approaches 6 x+6/(x-6)^2

OpenStudy (anonymous):

\[\lim_{x \rightarrow 6}\frac{ x+6 }{ (x-6)^{2} }\]

OpenStudy (luigi0210):

@whpalmer4

hartnn (hartnn):

just plug in x= 6 in that

OpenStudy (anonymous):

But you get 0

hartnn (hartnn):

that in the denominator, not in numerator also. numerator = 12, right ? and whats anything positive/0 =.... ?

OpenStudy (anonymous):

0... BUT IT CAN'T BE THAT SIMPLE ? ! Don't you have to do other stuff...

OpenStudy (luigi0210):

@hartnn anything 0/x is 0 :) x/0 is undefined

hartnn (hartnn):

its not 0 (anything positive)/0 = +infinity!

OpenStudy (anonymous):

oh wait whops

OpenStudy (anonymous):

omg

OpenStudy (luigi0210):

Oops too

hartnn (hartnn):

and thats it! you don't need to do anything else...

OpenStudy (anonymous):

so does DNE works ?

hartnn (hartnn):

not undefined, here, it'll be +infinity

hartnn (hartnn):

anything positive/0 = +infinity anything negative/0 =-infinity

OpenStudy (anonymous):

there;s not answer for that in the multiple choice tho

OpenStudy (whpalmer4):

Here's a graph showing the approach from 5 and 7, should be clear that it gets big fast as you approach x = 6 :-)

hartnn (hartnn):

its not DNE, when left hand limit does not equal right hand limit, then we say the limit DNE. here, you are getting the limit as +infinity.

hartnn (hartnn):

what are the choices ?

OpenStudy (anonymous):

DNE, 6, -6, 0

OpenStudy (luigi0210):

Are you like barely learning limits?

OpenStudy (anonymous):

yeah x__x

hartnn (hartnn):

strange, none of them is correct....

OpenStudy (anonymous):

OHHH whpalmer

OpenStudy (luigi0210):

Ah then I've had to deal with before.. it's DNE @hartnn

OpenStudy (whpalmer4):

yeah, the limit is definitely \(+\infty\)

hartnn (hartnn):

if i have to go with one, i'll go with DNE

OpenStudy (luigi0210):

They do not take/learn infinity for limits yet

OpenStudy (luigi0210):

Not till later at least

OpenStudy (whpalmer4):

not enough time to do it/learn it right, but there will be time to do it over later, I guess...

hartnn (hartnn):

hmm...go with DNE then

OpenStudy (luigi0210):

Yup, DNE

OpenStudy (anonymous):

Wow ok thanks guise.. wait one more a similar question

OpenStudy (anonymous):

so i guess this one is also DNE ?

OpenStudy (luigi0210):

Try the conjugate first

terenzreignz (terenzreignz):

Infinity is just convenience, isn't it? I mean, an infinite limit... is no limit...

hartnn (hartnn):

shouldn't that be \(\sqrt x-\sqrt {49} \quad or \quad \sqrt x-7 ???\)

OpenStudy (anonymous):

you can't just plug in the number you have to change the equation so that the denominator is not equal to 0

OpenStudy (anonymous):

and then you have to plug in 6

hartnn (hartnn):

if the question posted is correct, then again just plug in x=49...

OpenStudy (luigi0210):

multiply by sqrt{x}+sqrt{49}

OpenStudy (whpalmer4):

@musiklover317 you can, if the numerator is not also 0. it's the indeterminate forms where you have to apply L'Hopital.

hartnn (hartnn):

but the numerator has sqrt 7 ! are you sure you copied the question correctly ??

OpenStudy (anonymous):

so you get DNE again... yeah it's the right question!

hartnn (hartnn):

then yes, just plug in x=49

OpenStudy (luigi0210):

@hartnn can I show you my process?

OpenStudy (anonymous):

interesting..

hartnn (hartnn):

yes, Luigi, you can show us how we will reach to DNE in this case also

OpenStudy (anonymous):

@whpalmer4 changing the equation will be the easiest and simplest way to think.

OpenStudy (whpalmer4):

now this one is a legit DNE — the limit is different from each side.

hartnn (hartnn):

@musiklover317 show us what you mean by solving it entirely by yourself..

OpenStudy (anonymous):

oh hey the answer is infinity

hartnn (hartnn):

right! +infinity for 1st and DNE for 2nd ...

OpenStudy (luigi0210):

@hartnn 's right

hartnn (hartnn):

oh, we all are correct ;)

OpenStudy (luigi0210):

OpenStudy (anonymous):

Haha @_@ Now i'm stuck on another question... Evaulate or determine that the limit does not exist for each the limites (a) lim x->d- f(x) (b) lim x->d+ f(x) (c) lim x->d f(x) for the given dunction f and the number d

hartnn (hartnn):

can you ask new question on every new post, please ?

OpenStudy (anonymous):

OH LOL OK sorrie do i post it now

terenzreignz (terenzreignz):

@hartnn You mean 'can you make a new post for every new question' right? :3

hartnn (hartnn):

yeah, same thing, thanks! and yes.

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