syms y t s Y F

F=laplace('diff(y(t),t,t,t)+diff(y(t),t,t)+diff(y(t),t)+y(t)=10*exp(-3t)',s);
F=subs(F,{'laplace(yt,t,s)'},{Y});
F=subs(F,{'y(0)','D(y)(0)','D(D(y))(0)'},{0,0,0});
Y=solve(F,'Y');
y=ilaplace(Y);
figure(1);ezplot(y,[0,1])