Hello, I've got the problem. Can any one help me with that error?

syms x(t)
D3x = diff(x, t, 3);
D2x = diff(x, t, 2);
Dx = diff(x, t);
eqn = diff(x, t, 2)+2*diff(x, t)+x == 2;
cond = [x(0)==0, diff(x, t)==0];
xSol(t) = dsolve (eqn,cond)

Warning: Number of equations greater than number of indeterminates. Trying heuristics to reduce to square system.

> In symengine

In mupadengine/evalin_internal

In mupadengine/feval_internal

In dsolve>mupadDsolve (line 334)

In dsolve (line 203)

Error using mupadengine/feval_internal

Unable to reduce to square system because the number of equations differs from the number of indeterminates.

Error in dsolve>mupadDsolve (line 334)

T = feval_internal(symengine,'symobj::dsolve',sys,x,options);

Error in dsolve (line 203)

sol = mupadDsolve(args, options);

Answer 1

[KSSV]

It looks there is some problem with conditions. Check the conditions. Without the conditions it is working fine.

syms x(t)
Dx = diff(x);
D2x = diff(Dx) ;
D3x = diff(D2x) ; 

eqn = diff(x, t, 2)+2*diff(x, t)+x == 2;
cond = [x(0)==0, diff(x, t)==0];
xSol(t) = dsolve (eqn)

xSol(t) = 

Answer 2

[Walter Roberson]

cond = [x(0)==0, diff(x, t)==0];

The first part of that sets a boundary condition. The second part of it says that the derivative of x(t) is zero, which is a second equation rather than a boundary condition. The only way to satisfy diff(x, t) == 0 is if x(t) is constant

You probably wanted Dx(0)==0 or similar