Find the general solution of this ODE:
d2ydt2+6dydt+9y=8e3t\displaystyle \frac{{{d}^{{2}}{y}}}{{{\left.{d}{t}\right.}^{{2}}}}+{6}\frac{{{\left.{d}{y}\right.}}}{{{\left.{d}{t}\right.}}}+{9}{y}=-{8}{e}^{{-{3}{t}}}
The solution will be of the form:
y(t)=Cy1(t)+Dy2(t)+yp(t)\displaystyle {y}{\left({t}\right)}={C}{y}_{{1}}{\left({t}\right)}+{D}{y}_{{2}}{\left({t}\right)}+{y}_{{p}}{\left({t}\right)}
so use C\displaystyle {C} and D\displaystyle {D} as the arbitrary constants.

y(t)=\displaystyle {y}{\left({t}\right)}=