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Math Help - Can't seem to get this right (integrals)

  1. #1
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    Can't seem to get this right (integrals)

    I'm using a new method learned in class and cannot apply it properly. I made the table of integration and then simplified but still got it wrong. Where did I go wrong?
    Attached Thumbnails Attached Thumbnails Can't seem to get this right (integrals)-integralbyparts4.png  
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  2. #2
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    I can't understand this method.The solution is this:Can't seem to get this right (integrals)-img.jpg
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  3. #3
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    the method is called tabular integration and it requires that you
    take antiderivatives in the e^{3x} column ...

    e^{3x}

    \frac{1}{3}e^{3x}

    \frac{1}{9}e^{3x}

    \frac{1}{27}e^{3x}
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  4. #4
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    I couldn't get the other problem so I'm trying a similar one. I am applying the tabular table of integration method correctly but did not get the correct result. Here is my second attempt.
    Attached Thumbnails Attached Thumbnails Can't seem to get this right (integrals)-tabularmethod4.png  
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  5. #5
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    your writing leaves much to be desired ...

    7x^2 - 4x ............... e^{5x}

    14x - 4 .................. \frac{1}{5}e^{5x}

    14 ........................ \frac{1}{25}e^{5x}

    0 ......................... \frac{1}{125}e^{5x}


    (7x^2-4x) \cdot \frac{1}{5}e^{5x} - (14x-4) \cdot \frac{1}{25}e^{5x} + 14 \cdot \frac{1}{125}e^{5x} + C

    e^{5x}\left(\frac{7x^2-4x}{5} - \frac{14x-4}{25} + \frac{14}{125}\right) + C

    your result is the same as mine ... why do you say it's wrong? (you did forget the constant of integration)
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  6. #6
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    Is it okay to do what I did with the denominator and turn the 1/5, 1/25 terms into 1/125, multiplied the numerators by the correct amount and then factored out 1/125?
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  7. #7
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    Quote Originally Posted by solidstatemath View Post
    Is it okay to do what I did with the denominator and turn the 1/5, 1/25 terms into 1/125, multiplied the numerators by the correct amount and then factored out 1/125?
    yes, it's ok.
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  8. #8
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    I'm going to have to see my teacher about this. I input my answer and it said it was wrong, then input yours and it said it was wrong only to say the correct answer was the one I gave in the first place.

    Thanks for your help, time to break some computers!
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