Uniformly continuous function (sequence)

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SUMMARY

The discussion focuses on proving the uniform convergence of the sequence of functions defined by \( F_n(x) = \int_0^1 t^n e^{xn} f(t) dt \) for a positive continuous function \( f \) on the interval [0, 1]. Participants conclude that \( \lim_{n\to\infty} F_n(x) = 0 \) for all real \( x \) and that this limit is uniform on bounded intervals [a, b]. However, the limit is not uniform on the entire interval (-∞, ∞), as demonstrated through counterexamples.

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  • Understanding of uniform convergence in the context of sequences of functions
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  • Study the concept of uniform convergence in more depth, focusing on definitions and theorems
  • Explore the Dominated Convergence Theorem and its applications in proving limits of integrals
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angst18
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Homework Statement


(This is my first post and I'm not sure why the Tex code isn't working, sorry).Suppose [itex]f[/itex]is a positive continuous function on [itex][1,0][/itex].For each natural number[itex]n[/itex] define a new function[itex]F_n[/itex] s.t.
[tex]F_n(x) = \int_0^1 t^ne^{xn}f(t)dt[/tex]

(a) Prove that [itex]lim_{n\to\infty}F_n(x) = 0[/itex] for all real [itex]x[/itex].
(b) Prove that the above limit is uniform on each bounded interval [itex][a,b][/itex].
(c) Determine with proof or counterexample wether or not the limit is uniform on [itex](-\infty, \infty)[/itex].

Homework Equations


The Attempt at a Solution



So, I know that what I'm supposed to do for part (a) is to show that the limit is uniform so that I can bring it into the integrand and evaluate. I even know how to do this in when there's only one variable, but the addition of a 't' as well as an 'x' has me stymied.
I know I'm supposed to fix [itex]f(t)[/itex]for [itex]t\in [0,1][/itex] and [itex]x[/itex] (still not sure if i have to do the cases where [itex]x[/itex] is neg/pos) and then show that the limit is independent of [itex]x[/itex] and [itex]t[/itex], but there's something I'm not getting, or I'm doing it in the wrong order, because I'm basically totally stuck.
Thanks in advance for any help.
 
Last edited:
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Hello angst18. Welcome to PF.

To get Tex to work:

After selecting "Preview Post", you need to click on your browser's "Refresh" button. Otherwise the display will not show the updated Tex image. Apparently some memory location doesn't get updated unless you do this.
 

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