Axis of symmetry X= 1, when x >; At 1, y decreases with the increase of x,

When X=0 and X=2, Y=0,

When X=3, y is at least =-3 on [0,3].

2、Y=(X-a)^2+ 1-a^2，

Axis of symmetry X=a, parabola opening is upward, when a≤- 1 and X=- 1, y is minimum =2+2a,

When-1

When a> is 1, X= 1, and the minimum value of y =2-2a.