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Calc Help, Rolle's Thm Maybe?

  1. Jul 25, 2006 #1
    Anyway, I've come across this problem that I can't figure out. It looks set up as a Rolle's Thm problem, but it just doesn't work out...

    Let f be a continuous function on [a,b] and differentiable on (a,b) for some a,b > 0. Suppose f(a) = f(b) = 0.

    Show that f'(c)=f(c)/c for some c between a and b.

    The thing is this is next to straightforward problems like the integral of xsinx and |3-2x|>1. Am I just missing something?

    I mean, I've spent about 3 hours looking for a similar problem/theorem in my Calc book; even just a pointer from someone who knows the answer would be great.
  2. jcsd
  3. Jul 25, 2006 #2


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    Use Rolle's theorem on g(x) = f(x)/x
  4. Jul 25, 2006 #3
    *smacks self hard*

    I can't believe I missed that, thanks.
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