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Evaluate this integral

  1. Jul 2, 2008 #1
    1. The problem statement, all variables and given/known data
    [tex]\int[/tex][tex]^{5}_{0}[/tex] 1+2x[tex]^{3}[/tex]


    2. Relevant equations

    answer is: 635/2

    3. The attempt at a solution
    Integrating the function I get this: 1/2(x+x[tex]^{}4[/tex])
    My answer when evaluating the limits =1/2(630)
     
  2. jcsd
  3. Jul 2, 2008 #2

    Hootenanny

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    You might want to re-check your integral. What is:

    [tex]\int 1 dx[/tex]
     
  4. Jul 2, 2008 #3

    arildno

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    Dearly Missed

    Why should an anti-derivative of 1 be 1/2x, rather than just x???
     
  5. Jul 2, 2008 #4
    [tex]\int1[/tex]=x
    [tex]\int 2x^3[/tex] = [tex]\frac{x^4}{2}[/tex],
    1/2[tex]\int[/tex]x+x^4
    I took (1/2) out of the [tex]\frac{X^{4}}{2}[/tex]
    (So, maybe I can't do that, I should leave it and evaluate at the limits using (x^4/2)?
     
  6. Jul 2, 2008 #5

    Hootenanny

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    Note that:

    [tex]x+\frac{1}{2}x^4 \neq \frac{1}{2}\left(x+x^4\right)[/tex]

    So yes, you need to evaluate:

    [tex]\left.\left(x+\frac{1}{2}x^4\right)\right|_0^5[/tex]
     
  7. Jul 3, 2008 #6
    I see where I went wrong, thank you for your help!!
     
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