Exploring the Limit of a Complex Expression

In summary, the problem is finding the limit of (1/sqrt(x+a)-1/sqrt x) as x approaches 0. The attempted solutions included using L'Hospitale's rule and rewriting the expression, but neither were successful. The book suggested the answer is a/2, but it was proven to be incorrect by the teacher. Therefore, the conclusion is that the limit does not exist.
  • #1
Nowshin
4
0

Homework Statement



lim (1/sqrt(x+a)-1/sqrt x)
x->0

Homework Equations



None

The Attempt at a Solution



Too many too be listed :P
 
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  • #2
Sometimes, a limit just doesn't exist. But you have to prove that it doesn't. I'm sure that you've determined that the first term is fine. So your problem arises in the second term. I think that a proof by induction using L'Hospitale's rule should do it (I mean repeated applications of the rule just make things worse and worse).
 
  • #3
Attempted solutions: "Too many too be listed "

Aaah, there's a (not the, as there may be others) rub - you need to show something you've tried before you receive any help. What types of things have you attempted?
 
  • #4
statdad said:
Attempted solutions: "Too many too be listed "

Aaah, there's a (not the, as there may be others) rub - you need to show something you've tried before you receive any help. What types of things have you attempted?

I tired using the L'Hospitale's rule, but it didn't help. The damned "x" won't go away!Then I tired to rewrite it as

1/sqrt(x+a)-1/sqrt x) = (sqrt x- sqrt(x+a) )/sqrt(x(x+a))

and tried multiplying both the numerator and the denominator with (sqrt x + sqrt (x+a) ).That didn't work either.

Pacopag said:
Sometimes, a limit just doesn't exist. But you have to prove that it doesn't. I'm sure that you've determined that the first term is fine. So your problem arises in the second term. I think that a proof by induction using L'Hospitale's rule should do it (I mean repeated applications of the rule just make things worse and worse).

BTW, the answer is supposed to be a/2 according to my book. Are you sure? The answer might be wrong, though.
 
Last edited:
  • #5
Unless I am missing something, but i don't see how it can possibly be a/2.

The function isn't defined for all x<0, so the left hand limit wouldn't exist?
 
  • #6
The book I use is quite crappy and has some wrong answers. :P
 
  • #7
I contacted my teacher and it seems Pacopag was right, the limit really doesn't exist. :D
 

What is the limit of a complex expression?

The limit of a complex expression is the value that the expression approaches as the independent variable approaches a certain value. It can also be thought of as the value that the expression "approaches" but does not necessarily reach.

Why is exploring the limit of a complex expression important?

Exploring the limit of a complex expression is important because it helps us understand the behavior of the expression at certain points and can also help us solve problems involving rates of change and optimization.

How can I determine the limit of a complex expression?

The limit of a complex expression can be determined by using various techniques such as algebraic manipulation, graphing, and evaluating the expression at different values of the independent variable.

What are some common types of limits in complex expressions?

Some common types of limits in complex expressions include one-sided limits, limits at infinity, and limits involving trigonometric or logarithmic functions.

Are there any restrictions on the values that the independent variable can approach in a limit of a complex expression?

Yes, there can be restrictions on the values that the independent variable can approach in a limit of a complex expression. These restrictions are typically mentioned in the problem or can be inferred from the context of the expression.

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