How to solve 6 nonlinear coupled equations with 6 unknowns by MATLAB?

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Madhulima Bhandari
Madhulima Bhandari 2015-2-24
评论： MJTHDSN 2018-4-12
Dear All, I would like to solve following equations by MATLAB. What would be the code?
x(2) +x(3) +x(5) +x(6) -6;
2*x(1) + 2*x(4) + 4*x(5) -12;
x(2) + 2*x(3) + x(4) - 6.5468;
1.280*x(4)*x(5)*(x(1)+x(2)+x(3)+x(4)+x(5)+1)-x(1)^3*x(2);
2.152*x(2)*x(4)-x(1)*x(3);
2.614*x(4)*(x(1)+x(2)+x(3)+x(4)+x(5)+1)-x(1)*x(2);

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回答（1 个）

Torsten
Torsten 2015-2-25
help fsolve
Best wishes
Torsten.
  1 个评论
MJTHDSN
MJTHDSN 2018-4-12
Dear Matlabers,
I have a similar question. FSOLVE help didn`t really help me.
Let`s assume the equations as below:
SN = rnd(5,1); a = SN(1); b = SN(2); c = SN(3); d = SN(4); e = SN(5); f = SN(6);
eq1 = a*((x(1)^2)*(x(2)^2)+(x(1)^2)*(x(3)^2)-2*x(1)*(x(2)^2)+(x(2)^2))-((x(1)^2)*(x(4)^2)-2*x(1)*(x(4)^2)+(x(4)^2)-(2*x(1)*x(4)*x(5))+(x(4)*x(5))+(x(5)^2)) == 0;
eq2 = b*((x(1)^2)*(x(2)^2)+(x(1)^2)*(x(3)^2)-2*x(1)*(x(2)^2)+(x(2)^2))-((x(1)^2)*(x(4)^2)+(2*x(1)*x(4)*x(5))+(x(5)^2)) == 0;
eq3 = c*((x(1)^2)*(x(2)^2)+(x(1)^2)*(x(3)^2)-2*x(1)*(x(2)^2)+(x(2)^2))-((x(4)^2)+(2*x(4)*x(5))+(x(5)^2)) == 0;
eq4 = d*((x(1)^2)*(x(2)^2)+(x(1)^2)*(x(3)^2)-2*x(1)*(x(2)^2)+(x(2)^2))-((x(1)^2)*(x(4)^2)-2*x(1)*(x(4)^2)+ (x(4)^2)-(2*x(1)*x(4)*x(5))-(x(4)*x(5))+(x(5)^2)) == 0;
eq5 = e*((x(1)^2)*(x(2)^2)+(x(1)^2)*(x(3)^2)-2*x(1)*(x(2)^2)+(x(2)^2))-((x(1)^2)*(x(4)^2)-(2*x(1)*x(4)*x(5))+(x(5)^2)) == 0;
eq6 = f*((x(1)^2)*(x(2)^2)+(x(1)^2)*(x(3)^2)-2*x(1)*(x(2)^2)+(x(2)^2))-((x(4)^2)-(2*x(4)*x(5))+(x(5)^2)) == 0;
here, a,b,c,d,e,f are numbers (0.43 for example). For now I consider them as SN(i):
I want to find x(1),...,x(5) values.
I have tried many ways but no solution was found.
Can you help me with my problem?
Best

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