-123-123=123+(-123)=0
-456-123+123-452=(-456)-[(-123)+123]-452
=(-456)-0-452
=(-456)-452
=--908
-789-(-421)+1258
=(-789)+421+1258
=(-368)+1258=890
tik nha
-123-123=-123+(-123)=-246
-456-123+123-452=-456+(-123)+123+(-452) =[(-456)+(-452)] + [(-123)+123] = -908+0=-908
-789-(-421)+1258=-789+421+1258=890
tick giúp mình nha! Thank nhìu