Help Please

[kaebun]

use limits to describe the behavior of f at values of not x in its domain
f(x)=-1/(x^2-4)

 

[stapel]

Have you found the values of x that are not in the domain of f(x)?

If so, how much further have you gotten? If not, where are you stuck?

Also, when you refer to "using limits", are you refering to using a limit argument (which isn't usually taught until calculus) or are you just supposed to take values closer and closer to the forbidden x-value, and see what you get?

Thank you.

Eliz.

 

[kaebun]

i found the ones not in the domain(that was the first part of the problem) what i don't get is the whole limit thing.. i have no clue, we use it alot and most of the time i fake it... which doesnt work to great on tests :wink: useing limits is the books words .. not mine

 

[stapel]

i found the ones not in the domain

Okay; what did you get?

what i don't get is the whole limit thing.

Okay, but what sort of method are you supposed to be using? (I can't see your book, so you'll have to tell me what is expected of you.)

Thank you.

Eliz.

 

[kaebun]

im not sure what you mean by method. i gave you exactly what the book says... do u want me to give you an example of how we do limits?
its like for f(x)=x
lim f(x)=-infinity
x -> -infinity

 

[stapel]

im not sure what you mean by method....do u want me to give you an example of how we do limits?

That could be helpful, yes. Thank you.

Eliz.

 

[kaebun]

i did at the bottom

for f(x)=x
lim f(x)=-infinity
x -> -infinity

 

[stapel]

You stated a limit ("the limit of this as that goes there is some value"). But what is the method you're using to find the limit value? Are you looking at graphs? Are you plugging in values closer and closer to the limit point? Are you using theorems and comparison tests and such?

What method are you using?

Thank you.

Eliz.

 

[kaebun]

mostly graphs

 

[stapel]

Okay, if you're finding limits by looking at graphs, then plug "y₁ = -1/(x² - 4)" into your graphing calculator, and look at the picture, and/or look at the TABLE values. (If necessary, ZOOM in or TRACE on the graph, or change the TBLSET settings to give a smaller increment for x.)

Is y going up to positive infinity, or down to negative infinity, or neither? ("The" limit depends on having the right-hand limit and the left-hand limit agreeing.)

(Note: Depending on the text, your book might just want an answer of "no limit", any time the limit isn't a finite value. You'll have to check your text and/or your class notes to determine this, though.)

Eliz.

 

[kaebun]

im still confused because the graph is funny it does go to positive infinity or -infinity continuosly... so were you saying the answer would be no limit?
there is nothing in my ook about this or in my notes... my teacher is not very good she does't teach us much and the book is badley written in my opinion...

 

[kaebun]

im sry im asking so many questions im just trying to understand this

 

[stapel]

there is nothing in my ook about this or in my notes.

Well, if this hasn't been covered in the text or in class, then I'm afraid there is no way to know what it expected of you. Sorry.

Eliz.