由数轴可知
a﹤b﹤0﹤c,a+b﹤0,a+c﹤0,b-a﹥0,b-c﹤0
|a+b|-|a+c|-|b-a|-|b-c|
=-(a+b)+(a+c)-(b-a)+(b-c)
=-a-b+a+c-b+a+b-c
=a-b