齐次方程5y''+4y'+3y=0
y=e^(-2t/5)*(C1cos22^0.5t/5+C2sin22^0.5t/5)
非齐次方程5y''+4y'+3y=e^(-t)
特解y=e^(-t)/5D^2+4D+3=e^(-t)/4
y=e^(-2t/5)*(C1cos22^0.5t/5+C2sin22^0.5t/5)+e^(-t)/4