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  1. #1 Help me please~ 
    Forum Ph.D. Heinsbergrelatz's Avatar
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    Can anyone help me with this question? i know its very simple, but im stuck;

    Solve the equation;



    thank you


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  3. #2  
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    Do you need to actually solve the equation, or just extract x?


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    whether extracting x or y, the idea is to get rid of the "d" sign with an integral.
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    Uh, sorry, a bit out of my league. Hope you get help, though.
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    Are you in high school or university? Can't help though, it's above my level as well.
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    Well, the equation is not conservative. I am willing to offer that much, Hahaha.

    Might I suggest you integrate each element and treat the x as a constant in the first term and treat y as a constant in the second? I'm not sure about the validity of this, but I'm not sure what your solving for either. The lack of it being conservative eliminates the option of trying to find a tangent plane. Also, evaluating it as a closed line integral would require area bounds.

    All in all, I'm not sure what to tell you either. I think you need to be a bit more specific with what you're looking for. What solution are you trying to get. Give a name or description.
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    What do you mean by solve the equation? Do mean find the set of points (x,y) for which that 1-form is zero?

    The equation is equivalent to the two simultaneous equations

    x^2y = 0

    x^3 + x^2 y - 2 xy^2 - y^3 = 0

    The first equation implies that either x=0 or y=0.

    If x=0, the second equation implies that y=0.

    If y=0, the second equation implies that x=0.

    Evidently, this differential form vanishes only at (0,0).
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    Quote Originally Posted by salsaonline
    What do you mean by solve the equation? Do mean find the set of points (x,y) for which that 1-form is zero?

    The equation is equivalent to the two simultaneous equations

    x^2y = 0

    x^3 + x^2 y - 2 xy^2 - y^3 = 0

    The first equation implies that either x=0 or y=0.

    If x=0, the second equation implies that y=0.

    If y=0, the second equation implies that x=0.

    Evidently, this differential form vanishes only at (0,0).
    Absolutely correct. (No surprise.)

    But this kid is in high school and I don't think he is really trying to find the set of points where a differential form vanishes.

    On the other hand I have not been able to figure out what he is tryng to find. He does not always start with a well-posed problem.
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    Absolutely correct. (No surprise.)

    But this kid is in high school and I don't think he is really trying to find the set of points where a differential form vanishes.

    On the other hand I have not been able to figure out what he is tryng to find. He does not always start with a well-posed problem.
    Yes the post by salsaonline is somewhat mysterious to me, because thats no what we have to do. though he might me right, the answer in the book does not correspond to his response. This question is under the chapter (differential equations) and i have alot of nasty questions in here, which for you(Dr.Rocket and salsaonline, and some others) may seem like an easy question. This is one of them, in which i find tricky(not hard). That early binomial question i asked was pretty hard, and i gave a proof for it, but it seems like no one is giving me a response. This question im still working on it, and i will try to show my workings, i would appreciate if experienced members can correct my workings(wherever mistakes are there).
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    Quote Originally Posted by Heinsbergrelatz
    Absolutely correct. (No surprise.)

    But this kid is in high school and I don't think he is really trying to find the set of points where a differential form vanishes.

    On the other hand I have not been able to figure out what he is tryng to find. He does not always start with a well-posed problem.
    Yes the post by salsaonline is somewhat mysterious to me, because thats no what we have to do. though he might me right, the answer in the book does not correspond to his response. This question is under the chapter (differential equations) and i have alot of nasty questions in here, which for you(Dr.Rocket and salsaonline, and some others) may seem like an easy question. This is one of them, in which i find tricky(not hard). That early binomial question i asked was pretty hard, and i gave a proof for it, but it seems like no one is giving me a response. This question im still working on it, and i will try to show my workings, i would appreciate if experienced members can correct my workings(wherever mistakes are there).
    You need to start by very clearly telling us what you are trying to do and by defining yourbterms and symbols. You have not done that in either case.

    For this problem salsaonline gave you the solution to the most reasonable interpretation of your post. But I am not surprised that you do not understand what he is talking about.

    You have a tendency to throw out a bunch of symbols and think everyone will understand and in fact understand the same way that you or your text do. That won't work. You have to put in some thought and explain what you mean. In this case you provided an equation in terms of differential forms -- and I am quite sure that you did not mean to do that since you don't know what a differential form is. Consequently salsaonline's correct response hits you as a complete mystery.

    I think you started with an ordinary differential equation. Make sure you copied it correctly. This does not appear at first blush to be readily solvable, but might be a separable equation that was mis-copied.
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    you need to start by very clearly telling us what you are trying to do and by defining yourbterms and symbols. You have not done that in either case.

    For this problem salsaonline gave you the solution to the most reasonable interpretation of your post. But I am not surprised that you do not understand what he is talking about.

    You have a tendency to throw out a bunch of symbols and think everyone will understand and in fact understand the same way that you or your text do. That won't work. You have to put in some thought and explain what you mean. In this case you provided an equation in terms of differential forms -- and I am quite sure that you did not mean to do that since you don't know what a differential form is. Consequently salsaonline's correct response hits you as a complete mystery.

    I think you started with an ordinary differential equation. Make sure you copied it correctly. This does not appear at first blush to be readily solvable, but might be a separable equation that was mis-copied.
    nothing is miscopied, its exactly how it is given in the book. and yes it is a separable equation. No details of Symbol or whatsoever are given.
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    Quote Originally Posted by Heinsbergrelatz
    . and yes it is a separable equation.
    Then separate it and integrate.
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    Then separate it and integrate.
    the whole point of asking this question was that i was having a trouble separating the equation, in other words "solve the equation"-thats how the book put it.
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  15. #14 Re: Help me please~ 
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    Quote Originally Posted by Heinsbergrelatz
    Can anyone help me with this question? i know its very simple, but im stuck;

    Solve the equation;



    thank you
    Separating the equation is simple. Take the integral, and separate it into two integrals, one with every term attached to "dx" and the other with all the terms attached to "dy" and solve it.



    and if I did this right, it implies only x has to equal 0 after integrating.
    Wise men speak because they have something to say; Fools, because they have to say something.
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    I believe that solving it that way would yield:



    But your statement otherwise still holds true regardless.
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  17. #16 Re: Help me please~ 
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    Quote Originally Posted by Arcane_Mathematician
    Quote Originally Posted by Heinsbergrelatz
    Can anyone help me with this question? i know its very simple, but im stuck;

    Solve the equation;



    thank you
    Separating the equation is simple. Take the integral, and separate it into two integrals, one with every term attached to "dx" and the other with all the terms attached to "dy" and solve it.



    and if I did this right, it implies only x has to equal 0 after integrating.
    "Separating" here mrans getting all the x's on one side and all the y's on the other.
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  18. #17 Re: Help me please~ 
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by Arcane_Mathematician
    Quote Originally Posted by Heinsbergrelatz
    Can anyone help me with this question? i know its very simple, but im stuck;

    Solve the equation;



    thank you
    Separating the equation is simple. Take the integral, and separate it into two integrals, one with every term attached to "dx" and the other with all the terms attached to "dy" and solve it.



    and if I did this right, it implies only x has to equal 0 after integrating.
    "Separating" here mrans getting all the x's on one side and all the y's on the other.
    Which, DrRocket, I believe you were correct to say that the equation appears inseparable. I do not think it is separable either.

    Alright, Heins, this is a homework problem from a book, as I believe you mentioned. It is under differential equations, but what is the preceding lesson about? Explain in moderate detail, for it may give us some idea on what you're supposed to be doing with the equation.
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    Could it be that the the problem was to find a potential whose differential was the given 1-form?

    If so, I don't think that's possible, since the 1-form is not closed.

    That is, if , then we would have to have , which is not the case.

    And yes, I know that the book would never phrase it in that manner, but you know what I mean Dr R.
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    okay thanks arcane, for trying to help me out, but the answer in the book does not give the answer you gave me. Rather, the answer involves logarithm, which implies that there is a reciprocal function that is to be integrated

    Alright, Heins, this is a homework problem from a book, as I believe you mentioned. It is under differential equations, but what is the preceding lesson about? Explain in moderate detail, for it may give us some idea on what you're supposed to be doing with the equation.
    hmwrk problem?? i dont think so, the book im using isnt even used in my school + IB HL mathematics do not have d.e. of this sort. Rather they would have questions of d.e such as this one; y=e^{\alpha x} show that this satisfies the following; dy/dx+kd^2y/dx^2+xy=... (this is just some random example i came up with, in which i have see in my textbook.)
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    Quote Originally Posted by Heinsbergrelatz
    okay thanks arcane, for trying to help me out, but the answer in the book does not give the answer you gave me. Rather, the answer involves logarithm, which implies that there is a reciprocal function that is to be integrated
    If you are really interested in becoming a mathematician you would do well to concentrate less on finding the answer in the back of the book and more on understanding the nature of the question.
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  22. #21  
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    q.
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  23. #22  
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    If you are really interested in becoming a mathematician you would do well to concentrate less on finding the answer in the back of the book and more on understanding the nature of the question.
    well, i have solved it, and have arrived at what the answer in the book got. You really think im just mindlessly depending on the answer of the book? of course not. Also those answers at the back have a pretty small chance of going wrong. i also dont usually look at the answer, i look at it when im really fed up, and just stuck hopelessly. Of course at times i go with what i have got, even though the answer in the book does not agree with my answer.

    You see in my other post higher derivatives, i gave the answer at that back of the book, and you got something else, so you thought that the book was wrong (exactly the same thing here), but actually i got what the answer in the book said.
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  24. #23  
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    Quote Originally Posted by Heinsbergrelatz
    You see in my other post higher derivatives, i gave the answer at that back of the book, and you got something else, so you thought that the book was wrong (exactly the same thing here), but actually i got what the answer in the book said.
    Nobody here commented on the answer in the book, In fact nobody here could figure out what question you were really asking -- including 2 Ph.D. mathematicians.

    The answer given you by salsaonline is correct (he is one of the Ph.D.s), but pretty clearly did not address the question as you see it.

    My comment stands, in spades.
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    Nobody here commented on the answer in the book, In fact nobody here could figure out what question you were really asking -- including 2 Ph.D. mathematicians.

    The answer given you by salsaonline is correct (he is one of the Ph.D.s), but pretty clearly did not address the question as you see it.

    My comment stands, in spades.
    i dont get what you dont understand, i gave a question form my book, exactly the way it is in the book. Its asking you to solve it, and i also have said that the answer should come in a form of a separable d.e. . I have read what Salsaonline said again, and yes that also can be the solution. But im saying that thats not the answer the book is looking for, i mean in this chapter of Differential equations, you have to try and eliminate the dy and the dx so you only get functions in terms of x and y, and maybe sin cos arcos arctan log,ln etc... but the key idea is to get rid of the d's. So eventually the answer should come about as y=......
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  26. #25  
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    Quote Originally Posted by Heinsbergrelatz
    Nobody here commented on the answer in the book, In fact nobody here could figure out what question you were really asking -- including 2 Ph.D. mathematicians.

    The answer given you by salsaonline is correct (he is one of the Ph.D.s), but pretty clearly did not address the question as you see it.

    My comment stands, in spades.
    i dont get what you dont understand, i gave a question form my book, exactly the way it is in the book. Its asking you to solve it, and i also have said that the answer should come in a form of a separable d.e. . I have read what Salsaonline said again, and yes that also can be the solution. But im saying that thats not the answer the book is looking for, i mean in this chapter of Differential equations, you have to try and eliminate the dy and the dx so you only get functions in terms of x and y, and maybe sin cos arcos arctan log,ln etc... but the key idea is to get rid of the d's. So eventually the answer should come about as y=......
    You are confusing mathematics with arithmetic (computation).
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  27. #26  
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    of course the concept is there, but the computation is also there. hence im not confusing anything(arithmetic is also regarded as mathematics).
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  28. #27  
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    Quote Originally Posted by Heinsbergrelatz
    of course the concept is there, but the computation is also there. hence im not confusing anything(arithmetic is also regarded as mathematics).
    You have two choices:

    1) You can get you hackles up, let your ego get in the way,think you know better and keep arguing.

    or

    2) You can listen to people who understand a hell of a lot more mathematics than you do and learn something.

    Your choice.

    But you have an opportunity, and I think the capability to profit if you take option 2.
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    Quote Originally Posted by Heinsbergrelatz
    okay thanks arcane, for trying to help me out, but the answer in the book does not give the answer you gave me. Rather, the answer involves logarithm, which implies that there is a reciprocal function that is to be integrated

    Alright, Heins, this is a homework problem from a book, as I believe you mentioned. It is under differential equations, but what is the preceding lesson about? Explain in moderate detail, for it may give us some idea on what you're supposed to be doing with the equation.
    hmwrk problem?? i dont think so, the book im using isnt even used in my school + IB HL mathematics do not have d.e. of this sort. Rather they would have questions of d.e such as this one; y=e^{\alpha x} show that this satisfies the following; dy/dx+kd^2y/dx^2+xy=... (this is just some random example i came up with, in which i have see in my textbook.)
    You completely missed the point. Homework problems are homework problems regardless of the status of the book's use. You are using it, you implied that it was a problem posed in the book with a solution contained in the book. Calm down. What did the preceding lesson entail?
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