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

3 views (last 30 days)
Pablo Alonso on 24 Jan 2023
Answered: Walter Roberson on 24 Jan 2023
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 dsolve (line 203)
Unable to reduce to square system because the number of equations differs from the number of indeterminates.
T = feval_internal(symengine,'symobj::dsolve',sys,x,options);
Error in dsolve (line 203)

KSSV on 24 Jan 2023
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) = Walter Roberson on 24 Jan 2023
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

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