Monotone conitnuous function - find limits

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SUMMARY

The discussion centers on the properties of monotonic continuous functions and their limits as they approach infinity. It establishes that if a function \( f \) is monotonic and continuous over the real numbers \( \mathbb{R} \), and the integral \( \int_{a}^{\infty} f(x)dx \) converges, then it follows that \( \lim_{x \rightarrow \infty} xf(x) = 0 \). The participants explore the conditions under which \( f(x) < \frac{k}{x} \) for any positive \( k \) and sufficiently large \( x \), emphasizing the necessity of proving convergence.

PREREQUISITES
  • Understanding of monotonic functions
  • Knowledge of continuous functions in real analysis
  • Familiarity with improper integrals and convergence
  • Basic limit theorems in calculus
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  • Study the properties of monotonic functions in detail
  • Learn about convergence criteria for improper integrals
  • Explore limit proofs using epsilon-delta definitions
  • Investigate the relationship between function behavior and asymptotic analysis
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Students and educators in calculus and real analysis, mathematicians focusing on limits and integrals, and anyone studying the behavior of monotonic continuous functions.

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Homework Statement


if f is monotonic and continues in R, and \int^{\infty}_{a} f(x)dx converges then
lim_{x \rightarrow \infty} xf(x) = 0


Homework Equations





The Attempt at a Solution


I know that if xf(x) converges at all then it has to convergs to 0. But how do I know that it converges?
Thanks.
 
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Can you show that for any positive value of k however small, that f(x)<k/x for all x>N for N sufficiently large? Hint: suppose it's not.
 
Thanks.
 

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