Calculus Question (regarding limits)

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.
Status
Not open for further replies.

Chris418

Junior Member
10+ Year Member
7+ Year Member
Joined
Aug 20, 2006
Messages
49
Reaction score
0

Members don't see this ad.
Hey,

I dont think im supposed to put this here, but im in dire need of help (i took calc 5 years ago).

lim (x->9) f(x)=(9-x)/(3-(x)^.5)

Any ideas... i know the answer is 6, just not sure how to derive it.

Thanks in advance.
 

BellyDancingDoc

Rump Shaker
10+ Year Member
5+ Year Member
Joined
Mar 13, 2006
Messages
491
Reaction score
7
Ummm, no homework quesitons allowed in the Pre-Allo forum.

But for whatever it's worth, some folks are petitioning to have a Pre-med Homework forum opened. Try doing a search for the discussion and then (nicely) pestering a mod... :)
 

Chris418

Junior Member
10+ Year Member
7+ Year Member
Joined
Aug 20, 2006
Messages
49
Reaction score
0
eh, its not really a homework question; i just can't figure it out and im getting irritated... my bad though.
 

Stroganoff

Full Member
15+ Year Member
Joined
Nov 6, 2003
Messages
44,528
Reaction score
29,101
Plug 9 in and you get the indeterminate 0/0, so then you use L'Hopital's rule!

(Are you seeing that it's 9-9=0 in the numerator and 3-√9=0 in the denominator?)
 

Chris418

Junior Member
10+ Year Member
7+ Year Member
Joined
Aug 20, 2006
Messages
49
Reaction score
0
Alright, awesome... thanks, i appreciate it.
 

pyrois

Full Member
10+ Year Member
Joined
Nov 22, 2006
Messages
673
Reaction score
2
Hey,

I dont think im supposed to put this here, but im in dire need of help (i took calc 5 years ago).

lim (x->9) f(x)=(9-x)/(3-(x)^.5)

Any ideas... i know the answer is 6, just not sure how to derive it.

Thanks in advance.

Sigh, I can't leave a fellow pre-medder in such peril

There's a whole bunch of ways to do the problem. The most direct approach is simply multiplying top and bottom by 3 + (x)^0.5

The denominator will become (9-x) which will cancel with the top and leave 3 + (x)^0.5 which is 6 when you plug in 9.

Alternatively you can do The French Hospital's rule (L'Hospital) and differentiate top/bottom.

*edit* somebody ninja'd my response:p oh well.
 

braluk

SDN Surgerynator
Moderator Emeritus
10+ Year Member
5+ Year Member
Joined
Apr 30, 2006
Messages
11,823
Reaction score
68
No homework questions here.
 
Status
Not open for further replies.
Top