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Homework Help: Qualative look at diffy Q

  1. Oct 23, 2013 #1
    1. The problem statement, all variables and given/known data

    The funciton with the given graph is a solution of one of the following differential equations. Decide which one is correct and justify your answer.

    So does anyone know how I can draw this so you guys can see? Like a web site? The graph is non linear it is increasing up to what looks like a y intercept of 1 then it decreases non linearly in the first quadrant. It still increases for a tiny bit after is crosses the intercept.

    2. Relevant equations

    A) y ' = 1+xy B) y' = -2xy C. y' = 1-2xy

    3. The attempt at a solution

    I say it is C because that eq would have a y int of 1 which is what my graph looks like. and would have a neg slope in the first quadrant. But I don't know.

    Anyone know a site so I can draw it so you can see?
  2. jcsd
  3. Oct 23, 2013 #2


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    It would? Why?
  4. Oct 24, 2013 #3


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    I think you are misunderstanding what is given. The graph of y' would have a "y intercept of 1" but the graph you are given is of y, not y'. In (c), if x and y are both between 0 and 1/4 (so in the first quadrant) 1-2xy> 0 so the graph of y is increasing.

    You can download, for free, a very nice graphing program at http://www.padowan.dk/
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