Limit of x/(sqrt(1+3x)-1) as x approaches 0

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Homework Help Overview

The original poster attempts to find the limit of the expression x/(sqrt(1+3x)-1) as x approaches 0, which involves understanding limit laws and algebraic manipulation.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the method of multiplying by the conjugate to simplify the expression. Questions arise about the results of this multiplication and the implications for the limit as x approaches 0.

Discussion Status

Some participants offer guidance on simplifying the expression, while others reflect on their attempts and mistakes in the process. There is recognition of a misunderstanding regarding the terms in the denominator, indicating a productive direction in the discussion.

Contextual Notes

Participants are navigating the challenge of handling a limit that results in an indeterminate form, and there is an emphasis on ensuring correct algebraic manipulation in the context of homework constraints.

KiwiKid
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Homework Statement


Find the limit of x/(sqrt(1+3x)-1) as x approaches 0.

Homework Equations


The limit laws.

The Attempt at a Solution


I'm really stuck. I've tried multiplying all of it by (sqrt(1+3x)+1)/(sqrt(1+3x)+1), but that didn't work. I can't seem to get that 0 out of the denominator. What am I missing?
 
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What did you get after doing that multiplication?
 
micromass said:
What did you get after doing that multiplication?

(x(sqrt(1+3x)+1))/3x. Or (x*sqrt(1+3x)+x)/3x if you will. But the 3x still goes to 0, so that doesn't seem to work.
 
KiwiKid said:
(x(sqrt(1+3x)+1))/3x. Or (x*sqrt(1+3x)+x)/3x if you will. But the 3x still goes to 0, so that doesn't seem to work.

You can simplify it: you have x is numerator and denominator.
 
micromass said:
You can simplify it: you have x is numerator and denominator.

Oh, wait! I realize what I did wrong. I'd seen that, yes, but made the stupid mistake of presuming that there would still be '2x' (instead of '3') left in the denominator. *slaps head* Thank you, micro. :smile:
 

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