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Homework Help: Need help with this

  1. Jan 18, 2009 #1
    need urgent help with this

    any ideas will be appreciated

    [tex]\int[/tex]x2(1-5x2)10dx

    tried all kinds of things, what i now think needs to be done is to change the differential to d(1-5x2) so that i wont have to open the (1-5x2)10 which i really dont want to nor do i think i am expected to.

    d(1-5x2)=-10xdx.... not really helping me :(
     
  2. jcsd
  3. Jan 18, 2009 #2

    Mark44

    Staff: Mentor

    Re: need urgent help with this

    I tried several approaches, among them substitution and integration by parts, but didn't seem to get anywhere with either of these.

    Another approach that seems promising is a trig substitution, using x = 1/sqrt(5) * cos(theta).

    Using this approach I was able to rewrite the integral as
    [tex]-1/25 \int cos^2(\theta) sin^{21}(\theta)d\theta[/tex]
    This could be rewritten as two integrals, both in powers of sin(theta). At that point, I would use a table of integrals.

    This approach might be beyond your present capabilities, but it's the only one I can think of that leads anywhere.
     
  4. Jan 18, 2009 #3
    Re: need urgent help with this

    You could just expand the integrand using the binomial theorem.
     
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