Check for missing argument or incorrect argument data type in call to function 'solve'.

syms x1 x2 x3

Y=solve('4.4*x1-2.5*x2+19.2*x3-10.8*x4=4.3', '5.5*x1-9.3*x2-14.2*x3+13.2*x4=6.8', '7.1*x1-11.5*x2+5.3*x3-6.7*x4=-1.8', '14.2*x1+23.4*x2-8.8*x3+5.3*x4=7.2')

Check for missing argument or incorrect argument data type in call to function 'solve'.

why does it give an error?

Answer 1

[KSSV]

syms x1 x2 x3 x4
eqn{1} = 4.4*x1-2.5*x2+19.2*x3-10.8*x4-4.3==0 ;
eqn{2} = 5.5*x1-9.3*x2-14.2*x3+13.2*x4-6.8==0 ;
eqn{3} = 7.1*x1-11.5*x2+5.3*x3-6.7*x4+1.8 ==0 ;
eqn{4} = 14.2*x1+23.4*x2-8.8*x3+5.3*x4-7.2==0 ; 


s = vpasolve(eqn{:}) ;
x1 = s.x1 ;
x2 = s.x2 ;
x3 = s.x3 ;
x4 = s.x4 ;

OR

syms x1 x2 x3 x4
Y=solve(4.4*x1-2.5*x2+19.2*x3-10.8*x4==4.3, 5.5*x1-9.3*x2-14.2*x3+13.2*x4==6.8, ......
        7.1*x1-11.5*x2+5.3*x3-6.7*x4==-1.8, 14.2*x1+23.4*x2-8.8*x3+5.3*x4==7.2)

[Walter Roberson]

Right.

The reason it gives an error is that that form of solve was supported until roughly r2017a, but has not been supported since then. Now only dsolve() supports quoted strings and that is expected to end soon.