# how to create a function to solve a series of equitions?

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Zhe Dong on 8 Apr 2024
Commented: Zhe Dong on 8 Apr 2024
Hi Matlab users,
I want to write a function to help me solve a series of equtions, however I'm not sure how to achieve that. here's an example. The problem is that I want to calculate the unknowns 'a','b,'c', so I need to put it in the output of the function, in the mean time they are in the equtions, so I need to define them in the function, but how to define them if they are unkonwns?
function [a,b,c] = EqSol(var1,var2,var3,var4,var5,var6)
eq1 = a + b + c == 1;
eq2 = var3 == var1*a + var2*b;
eq3 = var6*var3 == var4*var1*a + var5*var2*b + c;
eqn = [eq1,eq2,eq3];
S = solve(eqn,[a,b,c]);
end

VBBV on 8 Apr 2024
if you have symbolic toolbox then you can define it inside the function as
function [a,b,c] = EqSol(var1,var2,var3,var4,var5,var6)
syms a b c
VBBV on 8 Apr 2024
Edited: VBBV on 8 Apr 2024
After solving the equations then return the outputs as
a = S.a
b = S.b
c = S.c
Assuming varx ...1,,6 are known values
Zhe Dong on 8 Apr 2024
yes that works, many thanks for the help!

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