Conjugate Limit: $\frac{\sqrt{x}-1}{x-1}$

In summary, the limit of the expression $\lim_{x\to 1}\frac{\sqrt{x}-1}{x-1}$ is equal to $\frac{1}{2}$, as shown by the solution provided using the conjugate and simplification. While LHopital's rule could also be used, it may be considered overkill in this situation.
  • #1
walker242
12
0
$\lim_{x\to 1}\frac{\sqrt{x}-1}{x-1}$

Homework Statement


Calculate the limit of [tex]\lim_{x\to 1}\frac{\sqrt{x}-1}{x-1}[/tex].

Homework Equations


As above.

The Attempt at a Solution


Have tried to multiplicate with the conjugate.
 
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  • #2


Have tried to multiplicate with the conjugate.

Ok, what did you get? Note that you must show your work in order to get help here.
 
  • #3


[tex]\lim_{x\to 1} \frac{\sqrt{x}-1}{x-1} = \lim_{x\to 1} \frac{\left(\sqrt{x}-1\right)\left(\sqrt{x}+1)}{\left(x-1\right)\left(\sqrt{x}+1\right)} = \lim_{x\to 1} \frac{x-1}{x\sqrt{x}+x-\sqrt{x}-1} = \lim_{x\to1}\frac{x-1}{\sqrt{x}\left(x-1\right)+x-1} = \lim_{x\to1}\frac{x-1}{(x-1)(\sqrt{x}+1)} = \frac{1}{2}[/tex]

So in essence, disregard me, for I am retarded. :P
 
  • #4


For a retarded person, remarkably good at limits!
 
  • #5


How about LHopital's rule?
 
  • #6


Why? That's like using a sledgehammer to crack a walnut. Walker242's solutions is excellent- especially because it is his solution!
 
  • #7


Why?
His solution is very good.
So I have no overriding reason; but LHopital is more generic.
But I am into generic, versus tricky.
 

Related to Conjugate Limit: $\frac{\sqrt{x}-1}{x-1}$

1. What is the purpose of a conjugate limit?

A conjugate limit is used to evaluate the limit of a function that may otherwise be undefined or indeterminate at a certain point. By manipulating the function with its conjugate, we can simplify the expression and find the limit more easily.

2. How do you find the conjugate of a function?

The conjugate of a function is found by changing the sign between the two terms in the numerator, i.e. changing a plus sign to a minus sign, or vice versa. For example, the conjugate of $\frac{\sqrt{x}-1}{x-1}$ would be $\frac{\sqrt{x}+1}{x-1}$.

3. When should I use a conjugate limit?

A conjugate limit should be used when evaluating the limit of a function that contains a radical in the numerator, as in the case of $\frac{\sqrt{x}-1}{x-1}$. It can also be used when evaluating the limit of a rational function with a complex denominator, such as $\frac{x+1}{x^2+1}$.

4. Can a conjugate limit be used to evaluate all limits?

No, a conjugate limit can only be used for certain types of limits, specifically those involving radicals or complex denominators. It cannot be used for limits involving trigonometric functions or exponential functions, among others.

5. How do you know if a limit can be evaluated using a conjugate limit?

If a limit involves a radical in the numerator or a complex denominator, then a conjugate limit can typically be used. However, it is always best to check the limit using other methods first, such as direct substitution or L'Hopital's rule, before resorting to a conjugate limit.

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