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I have a system of two equations in two variables $x$ and $y$.

$$\begin{align} F_1(a,b,c,d,e)x+F_2(a,b,c,d,e)y+F_3(a,b,c,d,e)&=0\\ G_1(a,b,c,d,e)x+G_2(a,b,c,d,e)y+G_3(a,b,c,d,e)&=0 \end{align}$$

I am pretty sure that they have a unique solution but I don't have a proof. The thing is that the coefficients are gigantic and Mathematica is taking forever to do a Solve. My guess is that it is checking to see if the system is not indeterminate or something.

Is there any way I can stop Mathematica from doing that and just solve it. I suppose I can suck it up and solve it by hand. I wanted to post the exact system but copy and paste is not working, I guess because it's too large. Each coefficient has maybe a hundred expressions in different combinations of about 10 variables. I need these expressions later when I will evaluate, plot, etc.

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Solve[ F1[a,b,c,d,e]x+F2[a,b,c,d,e]y+F3[a,b,c,d,e]==0&& G1[a,b,c,d,e]x+G2[a,b,c,d,e]y+G3[a,b,c,d,e]==0,{x,y} ] works perfectly fine for me. – phantomas1234 Aug 22 '12 at 22:29
Thanks phantomas1234. For me, since the expressions were gigantic, the comp was taking tens of minutes and still evaluating. – Amatya Aug 23 '12 at 18:57
Are you sure that you're providing the variables you want to solve for? It solves instantaneously for me. Or are you saying that you're actually trying to solve a much bigger system? – phantomas1234 Aug 23 '12 at 20:11

1 Answer

up vote 8 down vote accepted

I am probably missing something, but why not do

ans=Solve[{f1*x + f2*y + f3 == 0, g1*x + g2*y + g3 == 0}, {x, y}]

Mathematica graphics

and then ans/.f1->giganticexpressionwithabcdande, etc?

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:$ you're not missing anything. I'm a newb with mathematica. Thanks a lot! I'll try it and get back if something goes wrong. Thanks again. – Amatya Aug 22 '12 at 21:31
Ok, that worked. Thanks a lot ACL!! – Amatya Aug 23 '12 at 18:56

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