how do i solve a system of 5 equations

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bassam bitar 2015-7-19

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https://ww2.mathworks.cn/matlabcentral/answers/230405-how-do-i-solve-a-system-of-5-equations

评论： Star Strider 2018-10-17

采纳的回答： Star Strider

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Hi everyone

i am having problems solving for the following

y1=((2.117)*a+2*b-1691.45);
y2=((2.8235)*a-4*b-1935.22);
y3=(c+608.11-366.21-(0.666)*b+(0.7058)*a);
y4=(d+211.43-(0.33)*b-(0.5294)*a);
y5=(e-608.11-153.91-(0.666)*b-(0.4705)*a);

i have tried using the solve command in the toolbox but it keeps returning a as an undefined variable. a is an unknown and i need to solve for it and b c d e .

Any help would be appreciated !

Thanks !

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bassam bitar 2015-7-19

编辑：Walter Roberson 2015-7-19

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so this is the code i have so far but the answers are way off

syms a b c d e
equ1= (2.117)*a+2*b-1691.45 == 0;
equ2= (2.8235)*a-4*b-1935.22 == 0;
equ3= c+608.11-366.21-(0.666)*b+(0.7058)*a == 0;
equ4= d+211.43-(0.33)*b-(0.5294)*a == 0;
equ5= e-608.11-153.91-(0.666)*b-(0.4705)*a ==0;
sol=solve([equ1,equ2,equ3,equ4,equ5],a,b,c,d,e);
aSol = sol.a
bSol = sol.b
cSol = sol.c
dSol = sol.d
eSol = sol.e

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Answer 1

Star Strider 2015-7-19

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/230405-how-do-i-solve-a-system-of-5-equations#answer_186519

编辑：Star Strider 2015-7-19

在 MATLAB Online 中打开

You have to declare the symbolic variables first.

This works:

syms a b c d e 
y1=((2.117)*a+2*b-1691.45);
y2=((2.8235)*a-4*b-1935.22);
y3=(c+608.11-366.21-(0.666)*b+(0.7058)*a);
y4=(d+211.43-(0.33)*b-(0.5294)*a);
y5=(e-608.11-153.91-(0.666)*b-(0.4705)*a);
[a,b,c,d,e] = solve(y1, y2, y3, y4, y5, [a,b,c,d,e]);
a =  753.54
b =   48.101
c = -741.71
d =  203.37
e = 1148.6