Solving Linear System of Equations with a Real Parameter

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Gauss
Gauss el 30 de Nov. de 2019
Respondida: Steven Lord el 2 de Dic. de 2019
Hi, I'm a University Student, I never used Matlab and I have to solve with Matlab several Linear Systems of Equations with a Real Parameter, like this:CodeCogsEqn (1).png
λ∈ℝ
Since I really don't know anything about Matlab it would be great if there is some sort of Pre-Compiled code to solve this kind of Systems so every time I just have to replace the values in the equations and I can easily get the solutions I need.
Thanks a lot,
Have a nice one
  4 comentarios
Gauss
Gauss el 30 de Nov. de 2019
You are not the problem, disrespectful people are.
Every time I ask on a forum looking for help I get insulted.
Not the right way to behave, for sure.
If you know the answer to mi question though I'd appreciate it.
Thanks
Star Strider
Star Strider el 30 de Nov. de 2019
Editada: Star Strider el 30 de Nov. de 2019
@Gauss —
My pleasure.
Jim Riggs posted one that may be helpful.

Iniciar sesión para comentar.

Respuesta aceptada

Jim Riggs
Jim Riggs el 30 de Nov. de 2019
Editada: Jim Riggs el 30 de Nov. de 2019
Using the symbolic toolbox, you can solve it as follows:
1) Define symbolic quantities;
syms A B x1 x2 x3 x4 lamda
2) Write the problem in matrix form
A = [1 0 1 0; lamda 1 0 1; 1 1 1 1; 2 1 lamda 0; 0 0 1 1]; % 5 x 4 coefficient matrix
B = [x1; x2; x3; x4] % 4 x 1 column matrix
3) solve the system of equations
[v1, v2, v3, v4, v5] = solve(A*B==[1; lamda; 1; lamda; 1]);
The result:
v1 = value of x1
v2 = value of x2
v3 = value of x3
v4 = value of x4 and
v5 = value of lamda
I get two sets of solutions:
v1 v2 v3 v4 v5 = 0 0 1 0 0 and
v1 v2 v3 v4 v5 = 1 1 -1 0 1

Más respuestas (1)

Steven Lord
Steven Lord el 2 de Dic. de 2019
What do you know and what are you trying to find?
Do you know the value of λand you're trying to find the X values? If so, build your coefficient matrix and right-hand side vector and use the backslash operator (\) to solve the system. Both the coefficient matrix and right-hand side will include λ. See the documentation page for the mldivide function for more information.
Do you know the values of X and you're trying to find λ? If so, you could use fzero on one of the equations that involve λ.
Do you know neither λ nor the values of X and you're trying to find all five? In this case you don't have a linear system, you have a nonlinear system (due to the λ*X1 and λ*X3 terms) and so you'd need to use something like fsolve from Optimization Toolbox.

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