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Math Help - please help with integration

  1. #1
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    please help with integration

    integrate the problem

    integral(4x/sqrt(8x^2-1), dx, 2, 1)
    Attached Thumbnails Attached Thumbnails please help with integration-untitled.bmp  
    Last edited by taichi2910; April 9th 2009 at 05:26 PM.
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  2. #2
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    e^(i*pi)'s Avatar
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    What does the problem say? I do not want to download and open that document for security reasons
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  3. #3
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    Let u=8x^2+1, du=16x
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    Senior Member mollymcf2009's Avatar
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    Quote Originally Posted by taichi2910 View Post
    integrate the problem

    integral(4x/sqrt(8x^2-1), dx, 2, 1)
    \int^{2}_{1} \frac{4x}{\sqrt{8x^2-1}} dx

    Factor out your 4.

    4 \int^{2}_{1} \frac{x}{\sqrt{8x^2-1}} dx

    Do a substitution with:

    u = 8x^2-1

    du = 16x dx

    *Change your limits by plugging in your original limits into the equation for u

    \frac{1}{4} \int^{31}_{7} \frac{1}{u} du

    = [\frac{\sqrt{u}}{2}]^{31}_{7}

    Then evaluate!
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