# Limits question (multiple choice)

• Feb 19th 2008, 07:08 AM
XIII13Thirteen
Limits question (multiple choice)
I'm not really sure what it is asking me

lim -->5+ $\sqrt{5-x}=?$

The provided answers are

a.) not real
b.) 0
c.) 1
d.) none of these

I feel like it is 0. Since 5-5 is 0. Could someone help me here?
• Feb 19th 2008, 07:17 AM
ihmth
Is that all the informtion? I think it should give the value of x.
• Feb 19th 2008, 07:21 AM
XIII13Thirteen
That might be what is confusing me it does have $lim x---->5+$. The teacher said that is X from the positive side
• Feb 19th 2008, 07:28 AM
ihmth
so maybe the function is $\sqrt{5-x}$ and its asking for the value of the function as it approaches to 5. if that's the case, the answer will be 0.
• Feb 19th 2008, 08:42 AM
ihmth
wait, im not really sure about this. there is also a possibility that the answer will not be 0, because if you will graph it:

Attachment 5131
• Feb 19th 2008, 11:36 AM
XIII13Thirteen
That is a good point. I might just ask the teacher to clarify. I appreciate your help
• Feb 19th 2008, 12:02 PM
Plato
Quote:

Originally Posted by XIII13Thirteen
lim -->5+ $\sqrt{5-x}=?$
The provided answers are
a.) not real b.) 0 c.) 1 d.) none of these

Strickly speaking the answer would have to be (d.).
The function is not even defined for (5+).
However given how sloppy things have gotten, the expected answer may be (a).
• Feb 19th 2008, 12:03 PM
wingless
$\lim_{x\to 5^{+}} \sqrt{5-x}$

Graph:

http://img98.imageshack.us/img98/2015/graphwq6.gif

It's a one sided limit. What does it approach while x goes to 5 from left? It doesn't approach anywhere because f(x) isn't defined for $x>0$ !
• Feb 19th 2008, 12:42 PM
xifentoozlerix
The limit does not exist. By definition, the limit must be a real number. I agree with Plato in that the correct choice must be (d). To say "such and such limit is not real" would be a very ambiguous statement. Is it implying that the limit exists, but is not a real number?(Worried). Or, is it implying that "not real" is the same thing as "does not exist"? Either way, it is still worth clarifying with your teacher what he/she thinks is the correct answer so you don't get points taken off of an exam for being "too correct". It comes down to semantics.