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So I have a set of equations like 12 of them but 13 variables. However I would like to find the numerical value of the roots for the maximum value of a particular variable. I don't know how to do that so I would be grateful if somebody helps me. Here are the equations:

7.876174155966237*10^8 q[1] q[2]+3.089573929076111*10^11 q[1]* q[3]-1.383164420023547*10^11 q[1]*q[4]-8.69327863244762*10^10 q[1]* q[5]-5.782276395051118*10^10 q[1]*q[6]-3.882747274312769*10^10 q[1]* q[7]-2.718153431333784*10^10 q[1]*q[8]-1.871727631370937*10^10 q[1]* q[9]-1.160739768204187*10^10 q[1]* q[10]-8.06637222864757*10^9 q[1]*q[11]-5.963897903744298*10^9 q[1]* q[12]-4.915457539792909*10^9 q[1]*q[13]==41.572661478570835177915
8.23696667442628*10^8 q[3]*q[2]+3.089573929076111*10^11 q[1]* q[3]-3.14514257979788*10^11 q[3]* q[4]-1.364812421413417*10^11 q[3]*q[5]-8.200749083805965*10^10 q[3]*q[6]-5.199209763929092*10^10 q[3]*q[7]-3.48884718739484*10^10 q[3]*q[8]-2.32869468208448*10^10 q[3]*q[9]-1.380239079268908*10^10 q[3]*q[10]-9.323329484842843*10^9 q[3]*q[11]-6.754539699898449*10^9 q[3]*q[12]-5.502821647682379*10^9 q[3]*q[13]==39.090711539551680838935
8.61522790311153*10^8 q[4]*q[2]+3.14514257979788*10^11 q[3]* q[4]+1.383164420023547*10^11 q[1]*q[4]-3.018556794730371*10^11 q[4]*q[5]-1.251939130894869*10^11 q[4]*q[6]-7.200708200204837*10^10 q[4]*q[7]-4.581328545341369*10^10 q[4]*q[8]-2.95259803140547*10^10 q[4]*q[9]-1.660482187826396*10^10 q[4]*q[10]-1.086049100232898*10^10 q[4]*q[11]-7.691599943122406*10^9 q[4]*q[12]-6.186520887032309*10^9 q[4]*q[13]==39.71119902430646942368
9.04024901520535*10^8 q[5]*q[2]+3.018556794730371*10^11 q[4]*q[5]+1.364812421413417*10^11 q[3]*q[5]+8.69327863244762*10^10 q[1]* q[5]-2.662069346680555*10^11 q[5]*q[6]-1.084567931193396*10^11 q[5]*q[7]-4.58462119991434*10^10 q[5]*q[8]-2.954233262566902*10^10 q[5]*q[9]-1.086298309404161*10^10 q[5]*q[11]-7.692872367401133*10^9 q[5]*q[12]-6.187349069941687*10^9 q[5]*q[13]==43.43412393283520093215
9.58107308865949*10^8 q[6]*q[2]+2.662069346680555*10^11 q[5]*q[6]+1.251939130894869*10^11 q[4]*q[6]+8.200749083805965*10^10 q[3]*q[6]+5.782276395051118*10^10 q[1]*q[6]-2.416484550106671*10^11 q[6]*q[7]-1.000589953622153*10^11 q[6]*q[8]-5.667851443992393*10^10 q[6]*q[9]-2.71540993739268*10^10 q[6]*q[10]-1.613848374025927*10^10 q[6]*q[11]-1.070606507930378*10^10 q[6]*q[12]-8.3069156585462*10^9 q[6]*q[13]==66.30774855209701225155
1.023694674428333*10^9 q[7]*q[2]+2.416484550106671*10^11 q[6]*q[7]+1.084567931193396*10^11 q[5]*q[7]+7.200708200204837*10^10 q[4]*q[7]+5.199209763929092*10^10 q[3]*q[7]+3.882747274312769*10^10 q[1]* q[7]-2.335526899537523*10^11 q[7]*q[8]-9.170819378390439*10^10 q[7]*q[9]-3.868051931218125*10^10 q[7]*q[10]-2.128903059755466*10^10 q[7]*q[11]-1.341864327566713*10^10 q[7]*q[12]-1.013051826593238*10^10 q[7]*q[13]==59.676973696887311026395
1.09740654139634*10^9 q[8]*q[2]+2.335526899537523*10^11 q[7]*q[8]+1.000589953622153*10^11 q[6]*q[8]+4.58462119991434*10^10 q[5]*q[8]+4.581328545341369*10^10 q[4]*q[8]+3.48884718739484*10^10 q[3]*q[8]+2.718153431333784*10^10 q[1]*q[8]-1.632980324637583*10^11 q[8]*q[9]-5.906288180566143*10^10 q[8]*q[10]-2.944094061812386*10^10 q[8]*q[11]-1.737854910543447*10^10 q[8]*q[12]-1.267694594748506*10^10 q[8]*q[13]==59.676973696887311026395
1.226485374572291*10^9 q[9]*q[2]+1.632980324637583*10^11 q[8]*q[9]+9.170819378390439*10^10 q[7]*q[9]+5.667851443992393*10^10 q[6]*q[9]+2.954233262566902*10^10 q[5]*q[9]+2.95259803140547*10^10 q[4]*q[9]+2.32869468208448*10^10 q[3]*q[9]+1.871727631370937*10^10 q[1]* q[9]-1.319053049676902*10^11 q[9]*q[10]-5.363293427524359*10^10 q[9]*q[11]-2.756647166322137*10^10 q[9]*q[12]-1.87253921409798*10^10 q[9]*q[13]==30.3662534756404375
1.421056739280782*10^9 q[10]*q[2]+1.319053049676902*10^11 q[9]*q[10]+5.906288180566143*10^10 q[8] q[10]+3.868051931218125*10^10 q[7]*q[10]+2.71540993739268*10^10 q[6]*q[10]+1.661042505714571*10^10 q[5]*q[10]+1.660482187826396*10^10 q[4]*q[10]+1.380239079268908*10^10 q[3]*q[10]+1.160739768204187*10^10 q[1]* q[10]1.369382557754065*10^11 q[10]*q[11]-5.811111845727664*10^10 q[10]*q[12]-3.464461454834223*10^10 q[10]*q[13]==29.54554392224475
1.649776763694766*10^9 q[11]*q[2]+1.369382557754065*10^11 q[10]*q[11]+5.363293427524359*10^10 q[9]*q[11]+2.944094061812386*10^10 q[8]*q[11]+2.128903059755466*10^10 q[7]*q[11]+1.613848374025927*10^10 q[6]*q[11]+1.086298309404161*10^10 q[5]*q[11]+1.086049100232898*10^10 q[4]*q[11]+9.323329484842843*10^9 q[3]*q[11]+8.06637222864757*10^9 q[1]*q[11]-1.406003409468488*10^11 q[11]*q[12]-7.363054544339372*10^10 q[11]*q[13]==26.4268476193411375
1.926892257497436*10^9 q[12]*q[2]+5.811111845727664*10^10 q[10]*q[12]+2.756647166322137*10^10 q[9]*q[12]+1.737854910543447*10^10 q[8]*q[12]+1.341864327566713*10^10 q[7]*q[12]+1.070606507930378*10^10 q[6]*q[12]+7.692872367401133*10^9 q[5]*q[12]+7.691599943122406*10^9 q[4]*q[12]+6.754539699898449*10^9 q[3]*q[12]+5.963897903744298*10^9 q[1]*q[12]-1.636667034244436*10^11 q[12]*q[13]==27.5758409940951
2.169244191944226*10^9 q[13]*q[2]+3.464461454834223*10^10 q[10]*q[13]+1.87253921409798*10^10 q[9]*q[13]+1.267694594748506*10^10 q[8]*q[13]+1.013051826593238*10^10 q[7]*q[13]+8.3069156585462*10^9 q[6]*q[13]+6.187349069941687*10^9 q[5]*q[13]+6.186520887032309*10^9 q[4]*q[13]+5.502821647682379*10^9 q[3]*q[13]+4.915457539792909*10^9 q[1]*q[13]==9.5778412995448368

And variables are:

q[1],q[2],q[3],q[4],q[5],q[6],q[7],q[8],q[9],q[10],q[11],q[12],q[13]

I want to find other roots for the maximum value of q[2].

I know it is a bit complex but I don't know how to simplify it. Anyway I would be pleased if somebody could show me how to do that.

|improve this question
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  • $\begingroup$ Please read the second point in this answer ... and the whole thread aftearwads $\endgroup$ – Dr. belisarius Oct 26 '14 at 16:29
  • $\begingroup$ @belisarius Should I replace subscripted symbols with q_1, q_2... for example? $\endgroup$ – Starior Oct 26 '14 at 16:47
  • $\begingroup$ Much better with q[1], q[2], ...q[n] $\endgroup$ – Dr. belisarius Oct 26 '14 at 16:49
  • $\begingroup$ @belisarius Ok I fixed it. Thanks. $\endgroup$ – Starior Oct 26 '14 at 16:57
  • $\begingroup$ Welcome to Mathematica.SE! I suggest the following: 1) As you receive help, try to give it too, by answering questions in your area of expertise. 2) Read the faq! 3) When you see good questions and answers, vote them up by clicking the gray triangles, because the credibility of the system is based on the reputation gained by users sharing their knowledge. Also, please remember to accept the answer, if any, that solves your problem, by clicking the checkmark sign! $\endgroup$ – Dr. belisarius Oct 26 '14 at 17:51
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First put all your equations into a list (I'm not copying the full code here for brevity) 

eq = { eq1 == xx, eq2 == yy ...}

And then:

{val, sol} = NMaximize[{q@2, And @@ eq}, Array[q, 13], 
                       Method -> {"SimulatedAnnealing", "PerturbationScale" -> 10}];

sol // TableForm

Mathematica graphics

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  • $\begingroup$ Thanks for your answer. I did everything you said but it gave me this error: Syntax::tsntxi: "eq={7.876174155966237*10^8q[1]q[2]+<<21>>==41.572661478570835177915,<<1>>+<<21>>==<<24>>,<<8>>,<<1>>,2.169244191944226*10^9q[13]*q[2]+<<8>>+4.915457539792909*10^9q[1]*q[13]==9.5778412995448368}<<1>><<1>><<1>>" is incomplete; more input is needed. $\endgroup$ – Starior Oct 26 '14 at 17:47
  • $\begingroup$ Full code added $\endgroup$ – Dr. belisarius Oct 26 '14 at 18:14
  • $\begingroup$ I know this question is a bit old but I would like to ask something and I didn't want to open a new question for that. When I calculate the roots it gives me this error: NMaximize::nosat: Obtained solution does not satisfy the following constraints within Tolerance -> 0.001`... However, it also still gives me the solutions. May there be a chance that this error is making the solutions wrong? $\endgroup$ – Starior Nov 26 '14 at 10:36
  • $\begingroup$ @Starior Please open a new question and provide a link a to this one $\endgroup$ – Dr. belisarius Nov 26 '14 at 14:19

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