1、|a|= 2
a=±2
|x-1|= 3
x=4,-2
|2x-1|= 4
x=2.5,-1.5
|x+1|+|x-2|= 5
x=3,-2
|x+1|+|x-2|+|x+3|=3x+2,-2-3x,x+6