y=(x- 1)^2+2； Regarding 0, a, when x=0, the value is 3; It decreases monotonically at 0, 1, with a range of 3, and increases monotonically at 1, with a range of 2. Obviously, a is >; = 1; There are two maximum endpoint values, which is 3 when x=0; When x=a, a condition of 2-2a+3 < =3, a is obtained.