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Integration Technique

  1. Jan 24, 2013 #1
    I was working on a question and would this work?

    ∫3x^2*ln(x)

    After I did all of the math, I got to:

    ∫3x^2*ln(x)=x^3*ln(x)-x^3/3+c

    The problem I am having is not with the actual integration but another step I took:

    ∫3x^2*ln(x)=x^3*(ln(x)-1/3+c)

    I figured that -1/3+c just makes another constant so I left it as:

    x^3*(ln(x)+c)

    and distributing x^3 renders:

    x^3*ln(x)-c*x^3

    Is this process correct?
     
  2. jcsd
  3. Jan 24, 2013 #2
    No problem combining constants, HOWEVER - Why did you take that other step (from 2nd equation to third)? That is, why do you think that other step is correct?
     
  4. Jan 24, 2013 #3
    I now realize I was wrong. I factored out an x^3 even though it didn't have one making my conclusion worthless.
     
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