(II)证明:设C(x1,y1),D(x2,y2),Q(x,y),
∵ CP=-λ PD,∴(1-x1,3-y1)=-λ(x2-1,y2-3)
∴ 1-x1=-λ(x2-1)3-y1=-λ(y2-3),即 x1-λx2=1-λ(1)y1-λy2=3(1-λ)(2)
同理 x1+λx2=(1+λ)x(3)y1+λy2=(1+λ)y(4)
(1)×(3),得 x2 1-λ2 x2 2=(1-λ2)x(5)
(2)×(4),得 y2 1-λ2 y2 2=3(1-λ2)y(6)
(5)+(6),得 x2 1+ y2 1-λ2( x2 2+ y2 2)=(1-λ2)(x+3y)
∵C,D在圆O上,∴ x2 1+ y2 1=3,x2 2+ y2 2=3
∴3(1-λ2)=(1-λ2)(x+3y)
∵λ≠±1,∴x+3y=3
∴点Q总在定直线x+3y-3=0上.