nonlinear systems of equations

[moujail]

Hi everybody,

I am a biginner in Matlab (Release 13)
I have to resolve the following non linear systems of equations:

5.387=k1+k2+k3+3.92
0.022=sqrt{5.387-4*[k3*(3.92+k2)+k1*(k2+k3)]}
1.51326= {3.92+k1+k2+k4+sqrt[(3.92+k1+k2+k4)^2-4*k1*(k2+k4)]}/2
1.52376={3.92+k1+k2+k4-sqrt[(3.92+k1+k2+k4)^2-4*k1*(k2+k4)]}/2

May somebody help me???
Thanks

 

[Lagomorph]

use fsolve.

i wont be able to give the syntax better than the tutorial, so i suggest you try there, but here:

make an m file with your functions:
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function F = funcs(k)

F = [k(1)+k(2)+k(3)+3.92-5.387;
sqrt(5.387-4*(k(3)*(3.92+k(2))+k1*(k(2)+k(3))))-0.022;
(3.92+k(1)+k(2)+k(4)+sqrt((3.92+k(1)+k(2)+k(4))^2-4*k(1)*(k(2)+k(4))))/2 - 1.51326;
(3.92+k(1)+k(2)+k(4)-sqrt((3.92+k(1)+k(2)+k(4))^2-4*k(1)*(k2+k(4))))/2 - 1.52376;]

end
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in the command, you will need to make a starting guess. I will leave that up to you and just put all 1's.
-------------------------------------------------------
guess[1 1 1 1];
fsolve(@funcs,guess);
-------------------------------------------------------
I think this should work. Try it out. I think when you mean to use parenthesis, only use parenthesis. Dont use square or regular brackets. They denote something else entirely. Notice that I moved the values on one side of the equations to the other so that it equals 0. If this doesnt work, consult the Matlab help. Look up fsolve. I just started using it myself, so I might have missed something.