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From: Torsten Hennig on 12 Aug 2010 06:37
> Question
> How can i do that?
> I've been trying, solve, explot and subs.
> I can get the graph, but i cannot get the (x,y) pairs
> that I want.
>
> When I use function solve to solve the equation in
> term of x or y and then substitute the numeric value
> for one of them to find the other, I got the problem
> about complex numer. This might be because that
> numeric value that I substitute is not the number
> that satisfy the equation, so the program give me the
> result in complex number.
>
> Background.
> I need to use the pairs to find the optimal value of
> my objective function.
> I tried to use the fmincon, but it gave me the
> optimal value that is not reliable, so i try to do it
> manually.
> Note that my equality constraint is in the form of
> the equation in the subject.
> I also have a couple of inequality constraints.
>
> Thanks in advance

x^2+x+y^2+3y = 5y^2+3y+3xy+5
x^2+x(1-3y)+(-4y^2-5)=0
x^2-2x*(1.5y-0.5)-(4y^2+5)=0
x = 1.5y-0.5 +/- sqrt((2.25y^2-1.5y+0.25)+(4y^2+5))
x = 1.5y-0.5 +/- 0.5*sqrt(25y^2-6y+21)

So all points of the form
(1.5y-0.5 + 0.5*sqrt(25y^2-6y+21),y) or
(1.5y-0.5 - 0.5*sqrt(25y^2-6y+21),y)
for y in IR satisfy our equation.

Best wishes
Torsten.
From: Walter Roberson on 12 Aug 2010 12:53
Yeah basically, that what I want. But I need to obtain the value of
those pairs, because I want to use it to sub into my objective function
to find that which pair max my objective.

As Steve indicated, there are an infinite number of solution points.
Exactly how much RAM or disk space do you have to hold all of those
infinite results, and how long are you prepared to let your minimizer run?
From: Walter Roberson on 12 Aug 2010 16:04
Kittithad Wangveerathananon wrote:
> Could somebody help me on this, please?
> It may sound absurd, but i've been trying to do this for, like, many hours.

Sorry; next time something this important comes up, have your country's State
Department call our Ambassador, who will cable over to my country to get the
appropriate ministry to send someone over to my residence to wake me up.
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