括号前有加号,去掉括号不变号括号前有减号,去掉括号相反 (-9)+4+(-5)+8=-9+4-5+8=-2
(-9)+4+(-5)+8=-9+4-5+8=-2
(-9)+4+(-5)+8=4-9-5+8=-2
=-5-5+8=-10+8=-2
=8-9+4-5=-1-1=-2