1、特征方程 4r^2 +4r +1=0,r1=r2=-1/2,有重根,所以通解为y=(C1x+C2)e^(-x/2) y'=c1*e^(-x/2 )-(1/2)(c1x+c2)e^(-x/2 )=(1/2)(2c1-c2-c1*x)e^(-x/2 )y(0)=C2=2,y'(0)=1/2（2c1-2）=0得 c1=1,特解y=(x+2)e^(-x/2 )2、...
