求函數值域(15分)

h( x )= | 2x+3 | -3 | x-1 | + | x-2 | ,求函數值域
(a)
When x<= -3/2,
h(x) = -(2x+3) +3(x-1) -(x-2) = -4
(b)
When -3/2 < x <= 1
h(x) = (2x+3) +3(x-1) -(x-2) = 4x+2
-4 < h(x) <= 6
(c)
When 1 < x <= 2
h(x) = (2x+3) -3(x-1) - (x-2) = -2x+8
4 < h(x) <= 6
(d)
When x> 2
h(x) = (2x+3) -3(x-1) + (x-2) = 4
From (a),(b),(c) and (d),
函數值域 is [-4,6]