x''-2x'+2x=0特征方程r^2-2r+2=0r=1+i或 r=1-ix=C1e^tcost+C2e^tsint设方程特解x=(mt+n)e^tcost+(ut+v)e^tsintx'=me^tcost+ue^tsint +(mt+n)e^t(cost-sint)+(ut+v)e^t(sint+cost)=(m+n+v)e^tcost+(u-n+v)e^tsint+(m+...