f(x)=|x-2|+|x-4|-|2x-6|
(1) 2≤x≤3 f(x)=x-2+4-x-(6-2x)=2x-4∈[0,2]
(2) 3≤x≤4 f(x)=x-2+4-x-(2x-6)=8-2x∈[0,2]
(3) 4≤x≤8 f(x)=x-2+x-4-(2x-6)=0
综上:f(x)最大值为2,最小值为0
2+0=2
f(x)=|x-2|+|x-4|-|2x-6|
(1) 2≤x≤3 f(x)=x-2+4-x-(6-2x)=2x-4∈[0,2]
(2) 3≤x≤4 f(x)=x-2+4-x-(2x-6)=8-2x∈[0,2]
(3) 4≤x≤8 f(x)=x-2+x-4-(2x-6)=0
综上:f(x)最大值为2,最小值为0
2+0=2