x<-2，原式=(1-x)+(-x-2)+(4-x)=-3x+3-2≤x≤1，原式=(1-x)+(x+2)+(4-x)=-x+71x≥4，原式=(x-1)+(x+2)+(x-4)=3x-3
4种，❶当x＜-2❷-2≤x≤1❸1＜x≤4❹x＞4
