MATLAB: Errors during solving equations – sym/subsindex (line 796) and sym/subsref (line 841)

differential equationsequationfunctionfunction definitionindexingsymbolicsyms

Hello, I need to solve the equations, in order to find Cadt and Cbdt. My code is:
syms Cadt Cat Cbdt Cbt dt Maa Mab Mbb k ga gb KA KB KC 
eqn1 = (Cadt-Cat)/dt == Maa*(-k^2*ga - 2*(KA+KC)*k^4*Cadt - 2*KC*k^4*Cbdt) + Mab(-k^2*gb - 2*KC*k^4*Cadt - 2*(KB+KC)*k^4*Cbdt);
eqn2 = (Cbdt-Cbt)/dt == Mab*(-k^2*ga - 2*(KA+KC)*k^4*Cadt - 2*KC*k^4*Cbdt) + Mbb(-k^2*gb - 2*KC*k^4*Cadt - 2*(KB+KC)*k^4*Cbdt);
sol = solve([eqn1, eqn2], [Cadt, Cbdt]);
Sol1 = sol.Cadt
Sol2 = sol.Cbdt
However, I am getting theses errors:
Error using sym/subsindex (line 796)
Invalid indexing or function definition. When defining a function, ensure that the arguments are symbolic variables and the body of the function is a SYM expression. When indexing, the
input must be numeric, logical, or ':'.
Error in sym/subsref (line 841)
          R_tilde = builtin('subsref',L_tilde,Idx);
Error in Semi_implicit_conc_eqn_solve (line 8)
eqn1 = (Cadt-Cat)/dt == Maa*(-k^2*ga - 2*(KA+KC)*k^4*Cadt - 2*KC*k^4*Cbdt) + Mab(-k^2*gb - 2*KC*k^4*Cadt - 2*(KB+KC)*k^4*Cbdt);
It would be a great assistance if you let me know what went wrong in this code. Thanks a lot!

Best Answer

You forgot some multiplication operations when you defined formulas. MATLAB does not have any implied multiplication.
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