syms s t Y 
de = 'D(D(D(y)))(t) + 2*D(D(y))(t) - D(y)(t) - 2*y(t) = 4 + exp(2*t)'
ltode = laplace(de,t,s)
eqn=subs(ltode,{'laplace(y(t),t,s)','y(0)','D(y)(0)','D(D(y))(0)'},{Y,1,0,-1})
Y=solve(eqn,Y)
pretty(Y)
y=ilaplace(Y,s,t)
%diff(y,2)+2*diff(y,1)+y
%t=0; y_0=eval(y), Dy_0=eval(diff(y))
t = linspace(0,1,120);
z =subs(inline(y),t);
%ezplot(y),axis([0 1 0 2])