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Thread: Partial anti-deriv's: I get to -x^3 - x^2 y^2 - x^2 y^2 = c, but then I can't get ans

  1. #1

    Partial anti-deriv's: I get to -x^3 - x^2 y^2 - x^2 y^2 = c, but then I can't get ans

    Sorry to be posting the same sort of question again but I keep running into this issue and need to understand it. My latest encounter after taking partial anti-derivatives is:

    -x^3 - x^2 y^2 - x^2 Y^2 = c

    Collecting like terms and incorporating '-' into c:

    x^3 + 2 x^2 y^2 = c

    The book answer is:

    x^3 + x^2 y^2 = c

    Once again I do not understand why the 2 can be incorporated into c (assuming that is what was done).
    Last edited by stapel; 12-12-2017 at 03:26 PM. Reason: Splitting new question from existing thread to new thread.

  2. #2
    Elite Member stapel's Avatar
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    Quote Originally Posted by gw1500se View Post
    I keep running into this issue and need to understand it. My latest encounter after taking partial anti-derivatives is:

    -x^3 - x^2 y^2 - x^2 Y^2 = c
    So this is your result, after doing various other things to the original (and unknown-to-us) equation? Unfortunately, since we don't know how you arrived at this point, there is no way to know whether or not this is correct. Sorry.

    Quote Originally Posted by gw1500se View Post
    Collecting like terms and incorporating '-' into c:

    x^3 + 2 x^2 y^2 = c

    The book answer is:

    x^3 + x^2 y^2 = c

    Once again I do not understand why the 2 can be incorporated into c (assuming that is what was done).
    I can think of no possible (mathematically-legitimate) manner of "factoring" (?) the 2 out of one of the terms but not the other, somehow to "incorporate" it "into" the constant term.

    Please reply with the full and exact text of the original exercise, the complete instructions, and a clear listing of your thoughts and efforts which led to your beginning point above. Thank you!

  3. #3
    Thanks for the reply. I think you provided the answer or rather confirmed my suspicions. The book answer is just plain wrong and with the same error in more than one place. I know the result posted to that point is correct so there is no reason to take up time and space with the previous work. However, to see all the steps for a similar problem, please look at this thread.

    https://www.freemathhelp.com/forum/t...r-cos-%CE%98-1)

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