How to solve unknown number of equations

Question

Yagna V 2020-1-19

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https://ww2.mathworks.cn/matlabcentral/answers/500969-how-to-solve-unknown-number-of-equations

回答： Guru Mohanty 2020-1-25

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Let say I do not know the number of equation to be formed.

Let say I need n, the number of equations,

where n may vary from solving each time.

for i=1:n
    syms vi vi+1 v-1
    eqn i = (vi+1)^2+(vi-1)^2==20
end

So I get my n number of equation. However that won't work in matlab. Kindly suggest how to do the same.

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Answer 1

Guru Mohanty 2020-1-22

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Hi, I understand you are trying to create number of equations. You can do this using syms. Here is a sample code.

clc; 
clear all; 
n=input("Enter Number of Equations to be formed: "); 
syms v [1,n] 
for i=1:n 
    eqn(i) = (v(i)+1)^2+(v(i)-1)^2==20; 
    disp(eqn(i)); 
end 

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Yagna V 2020-1-22

thank you very much!

could you help me in solving the same equations with unknown variables

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Answer 2

Guru Mohanty 2020-1-25

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https://ww2.mathworks.cn/matlabcentral/answers/500969-how-to-solve-unknown-number-of-equations#answer_411972

在 MATLAB Online 中打开

Hi Yagna, You can solve the same equations using solve function in MATLAB.

Here is a sample code for it.

clc; 
clear all; 
% Forming Equation
n=2;
syms v [1,n] 
for i=1:n 
    eq(i) = (v(i)+1)^2+(v(i)-1)^2==20; 
    disp(eq(i)); 
end 
% Solving Equation
[v1_sol,v2_sol]= solve(eq,v);
disp(v1_sol);
disp(v2_sol);