Bài 108
- Nếu a > 0 thì –a < a và –a < 0.
- Nếu a < 0 thì –a > a và –a > 0.
Bài 111
a) (–13)+(–15)+(–8)
=–(13+5+8)
=–36
b) 500–(–200)–210–100
=500+200–210–100
=500+200–(210+100)
=700–310
=390
c) –(–129)+(–119)–301+12
=129–119–301+12
=(129+12)–(119+301)
=141–420
=–279
d) 777–(–111)–(–222)+20
=777+111+222+20
=(777+111+222)+20
=1110+20=1130.