y'+y/2=(1/2)e^(-x)其特征方程：r+1/2=0r=-1/2其通解y=Ce^(-1/2x)设其特解y=ae^(-x)y'=-ae^(-x)代入方程得-a+a/2=1/2a=-1其特解是y=-e^(-x)其解是y=Ce^(-1/2x)－e^(-x)
