y=-(x-1)²+1
函数图象开口向下,对称轴x=1
∴函数在(﹣∞,1]上单调递增,在[1,﹢∞)上单调递减
结合图象
(1)x∈R时y=-(x-1)²+1≤1
∴值域是(﹣∞,2]
(2)x∈[-2,0]时f(min)=f(-2)=-8,f(max)=f(0)=0
∴值域是[-8,0]
(3)x∈[-1,2] 时f(min)=f(-1)=-3,f(max)=f(1)=1
∴值域是[-3,1]
(4)x∈[2,4]时,f(min)=f(4)=-19,f(max)=f(2)=-8
∴值域是[-8,-19]