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#1 2010-07-18 03:15:43
- rogerkitkit123
- Guest
problem about limit
Show by means of an example that lim [f(x)g(x)]
x!a
may exist even through neither lim f(x)
x!a
nor lim g(x) exists.
x!a
#2 2010-07-18 03:17:59
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: problem about limit
Hi rogerkitkit123;
Can you please format the problem a little better? I can't read it at all. Might be browser related, I am sorry.
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#3 2010-07-18 03:21:33
- rogerkitkit123
- Guest
Re: problem about limit
limit absolute(f(x)g(x)) exist
but limit f(x) and limit g(x)
doesn't exist
#4 2010-07-18 03:53:30
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: problem about limit
Hi;
How about:
f(x) = 1 / x
g(x) = 1 / x^3
as x -> 0
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
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#5 2010-07-18 03:57:49
- rogerkitkit123
- Guest
Re: problem about limit
so f(x)g(x) is 1/ x^4
limit also not exist?
#6 2010-07-18 04:02:45
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: problem about limit
Yes, true, the limit approaches + infinity but that is not a number so the limit does not exist. Sorry, I had a halllllllluccccccination! I multiplied wrong!!!
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
Offline
#7 2010-07-18 04:04:56
- rogerkitkit123
- Guest
Re: problem about limit
quite a difficult question=(
#8 2010-07-18 04:15:08
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: problem about limit
Hi;
How about:
f(x) = tan(x)
g(x) = cot(x)
as x -> ∞
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
Offline
#9 2010-07-18 04:18:44
- rogerkitkit123
- Guest
Re: problem about limit
this one is great!!! thanks a lot=)
#10 2010-07-18 04:22:46
- bobbym
- bumpkin
- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 109,606
Re: problem about limit
Hi rogerkitkit123;
Welcome to the forum! Feels like there are more of them too!
In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.
Offline
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