Uncovering the Mystery of an Unlikely Limit Result

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  • Thread starter Thread starter Gib Z
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    Limit Mystery
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SUMMARY

The limit \lim_{x\to\infty} \sqrt{x^2+x} - x = \frac{1}{2} challenges conventional logic that suggests \sqrt{x^2+x} approximates to x as x becomes large. The error arises from neglecting lower-order terms, which can be addressed through rationalization or by using the binomial theorem for better approximations. The discussion emphasizes that understanding asymptotic behavior and error analysis is crucial for evaluating limits accurately.

PREREQUISITES
  • Understanding of limits in calculus
  • Familiarity with polynomial approximations
  • Knowledge of the binomial theorem
  • Experience with rationalizing expressions
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  • Study the binomial theorem and its applications in calculus
  • Learn about Taylor series for approximating functions
  • Explore techniques for rationalizing limits
  • Investigate asymptotic analysis and error estimation in calculus
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Students and educators in calculus, mathematicians focusing on limit evaluation, and anyone interested in deepening their understanding of asymptotic behavior in mathematical analysis.

  • #31
Gib Z said:
I don't really understand what I'm trying to prove..I know f is continuous, therefore all values are finite, as also shown by your theorem. Since f(x) is finite, and so is f(0), the error must also be finite. So to show that it is less than C|x| for some x we just have to choose a really large C, is that somewhat correct even if not rigorous?

You have to use the fact that f(x) is differentiable as well. Take the function f(x)=x^{1/3}. All values of this function are finite, but the function is not less than C|x| for any C whatsoever when x is sufficiently close to 0.
 

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