(r+1)(r2+1)2=0 特征根为F=-1,2==j,r==-, 故所求通解为 y=Ce +(C2+C3x)cosx+(C4+csx) x( 1)( 1) 0, 2 2 r + r + = 特征根为 1, , , 1 2 3 4 5 r = − r = r = j r = r = − j 故所求通解为 ( )cos ( )sin . y C1 e C2 C3 x x C4 C5 x x x = + + + + −