i am trying to solve ODE with the help of laplace transform, but it shows error in doing so, why?

syms x t s X

>> Dx = diff(x,t);

D2x = diff(Dx,t);

>> F=laplace(D2x+7*Dx+10*x(t)==20);

Error using sym/subsindex (line 864)

Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic variables,

and function body must be sym expression.

Error in sym/subsref (line 909)

R_tilde = builtin('subsref',L_tilde,Idx);

>>

Answer 1

[Swetha Polemoni]

Hi

The error is due to usage of x(t) before decalaring it . Try the following line of code.

syms x(t)

Hope this helps