How to Solve sytem of 7 equations with 6 unknown variables? How to combine any two equations? equations and variables given belowRequest for help
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Vijaya Kumar Kondagunta
il 27 Giu 2021
Commentato: Vijaya Kumar Kondagunta
il 30 Giu 2021
format short
syms eqn1 eqn2 eqn3 eqn4 eqn5 eqn6 eqn7 eqns sol p1sol p2sol p3sol p4sol p5sol p6sol p1 p2 p3 p4 p5 p6
eqn1 = -p1*0.00074+p2*30+ p5*2 + p6*0.2 == 0
eqn2 = p1*0.00062 - p2*30.00077 == 0;
eqn3 = p1*0.00012 +0.00031*p2 - p3*0.00012 == 0;
eqn4 = p2*0.00046 +p3*0.00012- p4*0.00063 == 0;
eqn5 = p4*0.0004 - p5*2 == 0;
eqn6 = p4*0.00023 - p6*0.2 == 0;
eqn7 = p1+p2+p3+p4+p5+p6==1;
% p1 to p6 above are 6 varaibles with 7 equations
% ? eqns = [eqn1, eqn2, eqn3, eqn4, eqn5, eqn7]
% ? sol = solve([eqns],[p1,p2,p3,p4,p5,p6]);
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David Goodmanson
il 28 Giu 2021
Hello Vijaya,
This is an overdetermined set of linear equations of the form M*x = b and can be solved in the least squares sense with the backslash function. The matrix M is (if I have not made a mistake)
M = [-0.00074 30 0 0 2 0.2
0.00062 -30.00077 0 0 0 0
0.00012 0.00031 -0.00012 0 0 0
0 0.00046 0.00012 -0.00063 0 0
0 0 0 0.0004 -2 0
0 0 0 0.00023 0 -0.2
1 1 1 1 1 1 ]
cond(M)
ans = 2.2943e+05
The condition number is large but not unreasonable. Then
b = [0 0 0 0 0 0 1]';
format short g
x = M\b
x =
0.45645
9.433e-06
0.45647
0.086954
1.7391e-05
9.9997e-05
concistency_check = M*x % compare with b
concistency_check =
1.2769e-17
7.3885e-18
-3.6135e-17
1.0916e-18
1.3783e-17
1.119e-18
1
This result is not so bad.
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