Find the limit as x approaches infinity of (sqrt(1+3x^2))/x

In summary, to find the limit as x approaches infinity of (sqrt(1+3x^2))/x, one can use l'hopital's rule or multiply and divide by x. Another method is to note that for arbitrarily large x, 3x^2 + 1 is approximately 3x^2. Additionally, one can also factor out a sqrt(x^2) from the numerator. However, it is important to note that this can only be done if two things are multiplied beneath a radical. Another approach is to say that as x gets arbitrarily large, sqrt(1+3x^2) becomes sqrt(3x^2) because the 1 becomes meaningless, resulting in a limit of sqrt(
  • #1
KevinL
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Homework Statement


Find the limit as x approaches infinity of (sqrt(1+3x^2))/x

The Attempt at a Solution


I tried using l'hopital's rule, but it gave me 3x/(sqrt(1+3x^2)) which doesn't help me at all.
 
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  • #2


use the fact that [itex]x= \sqrt{x^2}[/itex]
 
  • #3


Well, I can think of a couple of ways to do this one. Probably the simplest is to note that for arbitrarily large x, 3x^2 + 1 ~ 3x^2. Another way would be to multiply and divide the equation by x and then try to find the limit.
 
  • #4


Factor out a sqrt(x^2) from the numerator.
 
  • #5


JG89 said:
Factor out a sqrt(x^2) from the numerator.

I don't believe you can just do that. Only if two things are multiplied beneath a radical can something be taken out.

Multiplying by x/x does not help either.

Hmm, perhaps you can say that as x gets arbitrarily large, its sqrt(3x^2)/x because the 1 becomes meaningless and thus the limit is sqrt(3)?
 
  • #6


Yes you can do that! However, multiplying and dividing by x certainly does help: Lim (x -> infinity) sqrt(1/x^2 + 3)/1.
 
  • #7


KevinL said:
I don't believe you can just do that. Only if two things are multiplied beneath a radical can something be taken out.

Multiplying by x/x does not help either.

Hmm, perhaps you can say that as x gets arbitrarily large, its sqrt(3x^2)/x because the 1 becomes meaningless and thus the limit is sqrt(3)?



[tex]\sqrt(1+3x^2) = \sqrt(x^2(\frac{1}{x^2} + 3)) = \sqrt(x^2) \sqrt(\frac{1}{x^2} + 3)[/tex]
 
  • #8


Ah, clever. Thank you. Thats definitely how my prof would want me to do it.
 

FAQ: Find the limit as x approaches infinity of (sqrt(1+3x^2))/x

What is the limit of (sqrt(1+3x^2))/x as x approaches infinity?

The limit of this function as x approaches infinity is infinity.

How do you find the limit as x approaches infinity of (sqrt(1+3x^2))/x?

To find the limit, we can use the fact that as x gets larger and larger, the term with the highest power (x^2) dominates the other terms. Therefore, we can ignore the 1 in the numerator and the x in the denominator, and the limit becomes the same as the limit of sqrt(3x^2)/x. Simplifying this further, we get the limit as x approaches infinity of sqrt(3), which is infinity.

Is the limit of (sqrt(1+3x^2))/x an indeterminate form?

No, the limit is not an indeterminate form. Indeterminate forms occur when the limit cannot be determined by simple algebraic manipulation, but in this case, we can determine the limit by simplifying the expression.

Can we use L'Hopital's rule to find the limit as x approaches infinity of (sqrt(1+3x^2))/x?

Yes, we can use L'Hopital's rule to find the limit. By taking the derivative of the numerator and denominator, we get the limit as x approaches infinity of (3x)/sqrt(1+3x^2). As x approaches infinity, the denominator becomes larger and larger, causing the limit to approach infinity.

How does the value of the limit as x approaches infinity of (sqrt(1+3x^2))/x change if the function is multiplied by a constant?

The value of the limit remains the same regardless of the constant multiplied to the function. This is because, as x approaches infinity, the constant becomes insignificant compared to the term with the highest power (x^2).

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