2
$\begingroup$

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.

$\endgroup$
  • $\begingroup$ 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. $\endgroup$ – phantomas1234 Aug 22 '12 at 22:29
  • $\begingroup$ Thanks phantomas1234. For me, since the expressions were gigantic, the comp was taking tens of minutes and still evaluating. $\endgroup$ – Amatya Aug 23 '12 at 18:57
  • $\begingroup$ 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? $\endgroup$ – phantomas1234 Aug 23 '12 at 20:11
9
$\begingroup$

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?

$\endgroup$
  • $\begingroup$ :$ 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. $\endgroup$ – Amatya Aug 22 '12 at 21:31
  • $\begingroup$ Ok, that worked. Thanks a lot ACL!! $\endgroup$ – Amatya Aug 23 '12 at 18:56

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.