Find the particular solution of the differential equation
\(6 \frac{\mathrm{~d}^{2} x}{\mathrm{~d} t^{2}}+3 \frac{\mathrm{~d} x}{\mathrm{~d} t}+6 x=\mathrm{e}^{-t}\)
given that, when \(t=0, x=\frac{\mathrm{d} x}{\mathrm{~d} t}=0\).