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Homework Help: Lipschitz Problem

  1. Feb 22, 2010 #1
    Let f(x)=xp Show that f is Lipschitz on every closed sub-interval [a,b] of (0,inf). For which values of p is f uniformly continuous.

    So, we know that the map f is said to be Lipschitz iff there is a constant M s.t. |f(p)-f(q)|<=M|p-q|. And we were given the hint to use the Mean Value Theorem from calculus, which states f'(c)=(f(b)-f(a))/(b-a)

    I said choose (x,y) existing in [a,b], then |f(x)-f(y)|=|xp-yp|<=M|x-y|. But I am completely stuck here. I'm not sure how to define what M should be.
  2. jcsd
  3. Feb 23, 2010 #2
    Think of it geometrically: a Lipschitz constant [tex]M[/tex] is an upper bound for the largest (absolute value) slope of any line cutting the graph of [tex]f[/tex] in two points. The mean value theorem tells you how to estimate that largest slope.
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