a=-1.5 b=-1 c=0.5
|a+b|-|b-1|-|a-c|-|1-c|=???
先化简
|a+b|-|b-1|-|a-c|-|1-c|
=-a-b-(1-b)-(c-a)-(1-c)
=-a-b-1+b-c+a-1+c
=-2
等于负2
2.5-2-2-0.5=-2