empty sym: 0-by-1 for Simultaneous equation

1 view (last 30 days)
I'm trying to solve for these values but it keeps resulting in empty sym: 0-by-1. Any suggestions?
>> syms a b c d e x
>> equ1 = a + b == (0.83/12);
>> equ2 = c == (0.036/2);
>> equ3 = (0.048/16) + 2*0.21*x == 2*a + b + c + 2*d;
>> equ4 = 0.79*x == e;
>> equ5 = (a/(a + b + d + e)) == 0.109;
>> equ6 = (b/(b + a + d + e)) == 0.010;
>> equ7 = (d/(d + a + b + e)) == 0.071;
>> equ8 = (e/(e + a + b + d)) == 0.810;
>> sol = solve([equ1,equ2,equ3,equ4,equ5,equ6,equ7, equ8],[a,b,c,d,e,x]);

Answers (2)

Walter Roberson
Walter Roberson on 18 Jan 2021
You are trying to solve 8 equations for 6 variables, but they are not consistent for all 8 equations.
syms a b c d e x
equ1 = a + b == (0.83/12);
equ2 = c == (0.036/2);
equ3 = (0.048/16) + 2*0.21*x == 2*a + b + c + 2*d;
equ4 = 0.79*x == e;
equ5 = (a/(a + b + d + e)) == 0.109;
equ6 = (b/(b + a + d + e)) == 0.010;
equ7 = (d/(d + a + b + e)) == 0.071;
equ8 = (e/(e + a + b + d)) == 0.810;
sol = solve([equ1,equ2,equ3,equ4,equ5,equ6],[a,b,c,d,e,x]);
subs(equ7, sol), vpa(ans)
ans = 
ans = 
subs(equ8, sol), vpa(ans)
ans = 
ans = 

Shashank Gupta
Shashank Gupta on 18 Jan 2021
Hi Jacob,
If the solve function returns empty object then there is no solution exist for the given set of equations. I suggest you to check the feasibility of solution and equation first and then reform the equation and try.
Cheers.

Products

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!